'How To... Plan and Marshall a RIB Dive' Page

The information expressed herein should be treated as opinion. No guarantee is given or implied that any advice on the web-site is necessarily correct. Nor might it best suit other divers and clubs due to regional and personal differences. Diving is a risk sport - all advice herein should be validated with advice from your own diving club, governing body, or approved published material before being adopted.

How To...

… Plan a RIB Dive Trip

… Plan a RIB dive

All comments in "…Plan a general dive trip" apply. Special thoughts on RIB. Plan the diving for RIB abilities. Long sea trips a bad idea if: more than four or so divers; lumpy, windy or cold weather; separate waves of divers being taken; extreme diving being done; lone boat with single engine. Think about air. If compressor convenient during surface interval, get divers to take one cylinder (plus money for fills!). If not, take two and allow for effect on speed of extra weight. Carefully plan timings for state of tide at retrieval slip - make sure enough water at slip for safe easy retrieve when RIB will be back. Arrange who will tow the RIB to site and ensure access to boathouse. Make sure dive marshall can get access to box of electronics and trailer keys before the day. In electronics box must have: VHF Radio (check reception and report to coastguard on launching); GPS & antenna (log launch site co-ordinates); Echo sounder; Battery and backup battery; Equipment/transducer connector cable.

… Check the RIB safety equipment

Well before the day:

• Check Oxygen pressure in Oxygen kit and top up if necessary;
• Check first aid kit contents all present and in good condition;
• Check flares still in date;
• Charge VHF Radio battery;
• Charge main boat battery and top up backup battery.
• For engines, need:
  • 2 fuel tanks, plus a spare if planning a long boat journey;
  • 2 fuel lines;
  • Kill cords;
  • Spare prop, split pins and spanner;
  • Spare fuel line;
  • Spare spark plugs and plug spanner;
  • Spare starter cord.
• Ideally should also have:
  • Paddles;
  • RIB tube puncture repair kit;
  • Spare SMB reel and buoy;
  • A couple of spare ropes for boat towing etc.

… Prepare a shot line

Best to get this done before the day. Assess likely depth of wreck from books/charts. Allow for tide state. HW springs can add several metres, LW springs much shallower. Decide if can shot top of wreck and thus what depth from shot to surface.

• Measure out line to this depth plus only 10% or so (more than this will cause shot line to be angled and give long swim down). Fix main buoy here.
• Pay out two or three more metres and fix smaller telltale buoy.
• Fix shot or grapple to deep end with slightly weaker line so that if shot jams, only lose shot not whole line too.
• Loosely lay shot line into large bucket in boat from buoyed end first, shot end last.
• If deco dives being planned, fix carribiner or similar to line at stop depths for stage cylinders.
• If desired, also tie thin strong waster cord to bottom of shot line. This allows first divers to tie off shot line to wreck with waster to avoid shot being pulled off, but waster will break with strong pull to allow shot to be retrieved from boat.

… Prepare a break-free anchor

If critical to anchor firmly but likelihood of anchor getting stuck, make anchor break-free.

• Shackle anchor chain to nose of anchor.
• Run chain loosely along shaft.
• Fix nearest links to anchor eye with strong cable ties or thin strong cord.
• Anchor warp tied off to free end of remaining chain as normal.
• While anchor in use, cable ties pull anchor into sea-bed as normal and anchor bites.

In emergency, use very strong pulling or RIB engines to strain against anchor warp until cable ties snap. Chain then only fixed to nose of anchor. More pulling will then easily pull anchor flukes free and lift anchor nose-first.

… Marshal a RIB Dive

… Check RIB ready for trip

Before setting off check:

• Trailerboard lights all working;
• Trailer tyre pressures OK;
• Fuel tanks filled;
• Drain plug in.
• For trailer, should have:
  • Spare wheel;
  • Tyre pump;
  • Jack and wheel brace;
  • Wheel clamp and keys;
  • Spare light bulbs;
• For boat itself, must have:
  • Tube inflator foot pump and connector hose;
  • Anchor (one sand, one reef) plus anchor rope;
  • Coastal flare and smoke set (check still in date and not damp);
  • First aid kit;
  • Oxygen kit;
  • Diver down "A" flag;
  • Thunderflash diver recall signals;
  • Shot weight plus shot line,
  • Buoy and tell-tale buoy;
  • Fire Extinguisher.

… Get RIB tubes at right pressure

RIB has multi-compartment tubes. One valve per compartment. Make sure all are inflated evenly. Inflating one compartment bends the internal walls between compartments outwards. This seems to 'inflate' next compartment but strains inner wall. Important to pump all compartments evenly so inner walls stay fairly straight. If RIB/air cold, don't inflate fully - expands as warms up, but when about to launch make sure firm as cold water will contract air an deflate slightly. After dive check not too firm and let air out to prevent warmth over-pressuring tubes again.

… Tow the RIB safely

Important points are that speed limit is 60mph motorways, 50mph other roads if no local limits apply; and can't use outside lane of motorway if other lanes in service. Good idea to have clip-on extension wing mirrors to see behind you properly. More stable when towing if nose of trailer heavy, so put heavier kit in bow of boat.

… Set the RIB up at the launch site

Remove all transport straps, prop protectors, and untie painter from trailer. Fit GPS, echo sounder, VHF radio, and battery, then test. Remove spare wheel/jack etc and leave in someone's car. Connect fuel lines to engines. Open tank vents. Lift engines prior to launch so props clear. Check drain plug in. Check kill switches fitted securely. Pump up tubes if necessary (see "… Get RIB tubes at right pressure").

… Launch the RIB safely

Check engines raised. Normally best to launch RIB light and load heavy diving gear once afloat. If steep slip/sea-bed though, may get away with kit in boat during launch.

• Important to get one or more divers to guide you back, as impossible to see behind you & often children around slips.
• Gently reverse rib & trailer into water as far as possible without putting tow car at risk.
• Brake car securely. Ideally turn engine off and put into gear.
• Release winch strap and try rolling RIB off back of trailer. If water not deep enough, may be hard.
• Raise bow off trailer and try again. If still no good, release trailer from car and roll further into sea. RIB will float off OK then.
• While loading up but before engines started, radio coastguard with dive plan as in "…Radio coastguard with dive plan"). NB essential not to forget to radio again on return to say safely back.
• Care with "momentum trick" to get RIB off trailer quickly in shallow water. Release strap while still on slip. Roll car back into water then at last minute apply brakes sharply to roll RIB off trailer. Essential to have lookouts and be sure water deep enough for this. Must time it perfectly too. Take great care this way.
• Once launched and loaded, drop engines. Prime carburettors with line pumps and pull-start engines.
• As soon as started, check water coming from tell-tales and if not stop engines immediately. Running engines even for a few seconds without water can destroy coolant impellers and if for longer rapidly overheats engine and damages it.

… Radio coastguard with dive plan

Always try to notify coastguard of intentions before all dives. Example dialogue as follows.

• You: "Portland Coastguard, Portland Coastguard this is Chippenham Diver, Chippenham Diver -- over"
• C/g: "Chippenham Diver, this is Portland - change to channel six seven"
• You: "Portland this is Chippenham Diver - we'd just like to notify you of our dive plan for today, over"
• C/g: "Chippenham Diver this is Portland - go ahead, over"
• You: "Portland this is Chippenham Diver - we are a party of 6 divers, 5 experienced and 1 novice on a RIB. We've just launched from Bowleaze Cove. We'll be diving Lulworth Banks then a second dive at Ringstead Reef before returning to Bowleaze. Estimated time of return is around 15:30, over"
• C/g: "Chippenham Diver this is Portland - which part of the banks will you be on, over?"
• You: "Portland this is Chippenham Diver - we'll be fairly central, around the Lulworth Cove area, over"
• C/g: "Thank you Chippenham Diver - please let us know when you are safely back. Portland out."

… Avoid prop damage

Very easy to trash prop on rocks. Main avoidance is to know safe channels between slip and sea. Learn buoyage and get advice from locals. In all circumstances, keep eye on echo sounder and if gets below three metres or so take it very easy wherever you are. Learn to read sea surface.

• Sudden shallows increase local wave height and often lead to them breaking.
• Currents kick up over shoals and can be seen on surface.
• Colour of the water can vary with depth in some conditions.
• Once in shallows, don't rely on echo sounder to avoid prop damage - transducer is at rear of RIB so by time sounder screen shows too shallow, props will have already hit.
• Position a lookout on the bow to watch the sea-bed. If viz bad, have probe (paddle/flag pole) in water off the bow. As soon as lookout warns of shallows, shut throttle and take out of gear. Drift or paddle past obstruction until safe to re-engage props.
• For long distances in shallow water, get divers out and walk RIB to deeper water. With full trim/tilt engines, can also lift engines and operate props just below surface, though efficiency is awful.

… Use the GPS

Manual available. Read that first, but best way to learn is to use it. To get best out of it, find out Lat and Long of dive site and program this as waypoint before setting out. Get someone who understands GPS to show basics then try to use it to get to dive site.

… Use the Echo sounder

Again, manual available for basic operation but experience counts. Get used to display and what to look for on good sites. Biggest thing to understand is effect of different sea-bed depths.

• If scanning 40m deep, even small lumps in trace may be interesting.
• If only 6m deep, even big lumps can be small boring rocks.
• When pinpoint precision needed, remember that reading is from point of transducer (normally at rear of hull), so boat has already passed over whatever on screen. Do several passes if shotting a wreck so can predict best place to let shot go.
• For same reason, don't rely on echo sounder to avoid prop damage. Will be too late by time on screen (see "…Avoid prop damage"). Don't be fooled by big pings appearing on scan while divers down.
• Divers and even their bubbles reflect sonar and can seem like big wrecks or reefs - and deeper divers can be under boat even if SMB or surface bubbles are well away.

… Find interesting sea-bed

Best bet is to study books/charts and get co-ords beforehand. If just looking on spec, use simple rule of thumb: unless hunting flatfish, the more varied the se-bed depth, the more interesting the dive. Rare that ridges/gullies less than a metre or so are very interesting. Remember to look at numbers more than trace on sounder - depth variations on trace look shallower the deeper the sea-bed. Drop-offs often good. If known there's a drop-off/ledge in the area, generally ridges follow coastline so best to head straight out to sea (or straight for shore if on deep side) watching sounder. Normally, steeper walls better than gently sloping drop-offs, so try to find the most sudden changes in depth. When dropping divers in, make sure they know whether on high part or low part, and which direction to head to get to wall.

… Find a wreck

Research first. Look in books and on charts to get depths & locations. Need to get to close vicinity using GPS, transits, or triangulated compass bearings.

• Once in right area, set up search pattern, criss-crossing the area.
• Use GPS plot mode to see where RIB has been/is going.
• Watch echo sounder all the time. As soon as large disturbance seen, turn and criss-cross the wreck.
• Use GPS plot to see where main bulk of wreck is.
• Once best dive location identified, drop shot (see "…Deploy a shot line"). Very big wrecks in 30m or less and with current running (e.g. Aeolean Sky) can sometimes be located by sight. Currents well up over wreck and typically smooth the waves. Forms distinct patch of visibly different sea surface. Start looking up-current from this patch.
• Can also find wrecks closer inshore if one good transit by heading out to sea precisely along this transit and watching echo sounder carefully.
• For shallow wrecks, can also do snag search. Drop shot overboard and drag along sea-bed behind RIB. As soon as it snags, let go - that's probably the wreck. First divers down should make shot secure so it doesn't pull of wreck.

… Deploy a shot line

Mostly to do with timing. Get someone watching sounder and someone else to release shot.

• As soon as right part of wreck appears on sounder, yell release.
• Feed line quickly and make sure buoys don't snag as whole line plays out.
• Check shot in right position. If too much slack line, good idea to gently motor the RIB up current, gently reeling in spare shot line, then reposition buoy so line as vertical as possible without pulling shot off wreck.
• Useful if current running too fast - as on release, the buoy will be pulled under. When it surfaces, you know current slack is enough to dive.

… Drop divers in the water properly

Ensure divers completely ready to dive and checks complete.

• Run RIB up-current along shot line parallel to line of main buoy and tell-tale buoy and one or two metres away.
• Go past tell-tale buoy then on past main buoy for three or four metres.
• Then throttle back, take engine(s) out of gear and yell for divers to go.
• As divers drop in, will have enough time to get upright and drift onto main shot buoy. If divers miss the buoy and drift past it, do not just tow them back to it. Far too easy for diver to slip free and get chopped by props.
• If little current, good weather, no waves, no other dive boats around and not drifted far from shot, acceptable to tow a them in reverse only for a short distance at slow speed. This way if they slip free, the props move away from them. In all other situations, get them back into RIB, re-kit and do the drop run again.

… Secure shot line to wreck

In calm conditions with experienced divers, no need to. If risk of current or divers pulling shot off wreck, best to secure it. First pair down to descend without pulling on line. At bottom, can tie off shot with waster cord (see "…Prepare a shot line"). If shot weight is an anchor/grapple, better still to loop anchor back up and secure to shot line by flukes so no risk of snagging when waster breaks. Good idea too if first pair takes small signal float down to release when shot secure so other divers know when OK to use shot line. If no waster, have to have first pair wedge shot/anchor into wreck, then last pair release it so will pull out cleanly.

… Retrieve a shot line

As long as carefully pre-planned, last dive pair to come up can use as shot line as deco buoy. Free shot end completely from wreck and ascend up line. Divers drift with shot buoy and RIB tracks as for SMB. Vital that no risk of other divers left on wreck before doing this. Only safe way is if last pair were only pair of second wave.

• If all divers up before lifting, but shot jams, try motoring RIB round at different angles. At same time, apply strong tension then release totally.
• If no joy, will have to lose shot by breaking line free and leaving shot (assuming weak link at shot end - see "…Prepare a shot line").
• If shot comes free OK, can save much effort by "power lifting" it using RIB.
  • Have large buoy with wide diameter steel ring underneath.
  • Feed shot line through this and leave buoy free in water.
  • Pull loose end of shot line until taught.
  • Attach to RIB and motor off.
  • Water drag will keep big buoy from moving fast and RIB will pull shot line through the ring. Shot weight will come to surface. When weight hits buoy, just maintain tension and pull weight plus buoy to RIB.

… Track divers underwater

On drifts, divers must use SMBs. Never try to track on bubbles. Extremely easy to lose bubbles even in calm conditions. SMBs usually no problem, but can be an issue if no current and two pairs go in opposite directions. Can easily end up widely separated. Easy to lose sight of one SMB here - especially in swells. Best avoidance is to tell divers which way to go so all go same way. If happens anyway, try to track both by shuttling between and using GPS to track positions. As soon as any hint this is getting hard, must recall at least one pair of divers. Far too dangerous to just hope to be able to find second pair after first pair surface. Don't forget too that second pair can drift a long way just while getting first pair into RIB. Don't take risks. Short dives far better than lost divers.

… Recall divers in an emergency

If several divers down and divers surface in trouble, or for any reason RIB has to leave site urgently (e.g. to answer Mayday, or sudden worsening of weather), may need to get remaining divers up in a hurry. If diving with SMBs, troll round buoys (great care needed as divers may be surfacing) and give agreed signal by tugging on lines. Club standard is four strong tugs. Can also use Thunderflash signals. If no other method available, go near to divers and rev RIB engines repeatedly - divers often take this to mean cover boat getting impatient.

… Pick up RIB divers

• If no wind, better if divers separate and let RIB go between them. That way more space to get them into boat from opposite sides. If windy, better if both on same side of boat so RIB can approach up-wind to be blown toward divers when engines cut.
• If divers surface in wind and well apart anyway, approach upwind of both and let RIB blow toward them. Approach very slowly once close then as soon as no doubt they will connect with RIB, throttle back and knock out of gear. (RYA recommends killing engine, but club recommends leave idling so no risk of not re-starting). If one diver connects but other starts drifting away, get one diver in quickly then go for other.
• Only if positions right and conditions good, acceptable to tow first diver in reverse gear only and at very low speed to get second diver to boat. Under no circumstances tow a diver in forward gear. Otherwise, release first diver again, tell them to swim towards each other then do another approach run.
• While picking up divers, always keep watching out for other boats and other divers surfacing.

… Retrieve the RIB

On way back, make sure as much water out of RIB as possible. Once back at slip, best to unload heavy gear and walk it to shore before retrieving RIB. Only in calm conditions with good grippy slip and deep water at base of slip will laden retrieve work. Rarely even worth trying.

• Kill engines and lift out of water.
• Back trailer into water as far as possible without putting tow car at risk.
• Unwind winch strap and hitch to RIB bow eye.
• Align hull carefully with rollers and winch onto trailer. If gets hard near end of travel, sometimes helps to lift nose of trailer high, winch RIB on and pull trailer back down.
• Hitch trailer to car and tow out of water and drop engines back down. If slip base shelves too gradually to float RIB onto trailer, try manually pushing trailer out into deeper water and winching RIB on there. Attach rope from trailer to tow car on slip.
• Tow RIB to base of slip. Important now to stop, chock trailer with rocks, and bring car back down slip to attach trailer properly.
• Very hard to control a trailer attached by long rope - dangerous: don't do it.
• Once back in car park, remove electrics, refit straps, tie painter round trailer nose as security, strap tiller to side of RIB to stop it swinging in transit, attach prop covers, and remove drain plug to let any water out from hull. Refit before setting off to prevent loss.

… Refill the RIB fuel tanks

Important to refill tanks fully after every expedition. Only fair way to make sure fuel costs apportioned to the right divers. Make sure oil mix is right. Fill tanks nearly full but leave a bit of a gap. Note the number of litres of fuel used. Add 10ml of oil for every litre of fuel. E.g. if 15 litres put in tank, add 150ml oil. Screw down vents securely to avoid water ingress during storage.

… Divvy up RIB dive costs

Main costs to split are:

• towing costs (petrol consumption vastly higher when towing, so often biggest cost),
• slip fees (typically £5-12 if not free),
• RIB petrol costs (depends entirely on how heavily RIB been used - anywhere between 20 and 60 litres / £12 to £35), and parking dues for towing car.
  
• So, dive marshall normally tots up all chargeable costs, divides it by number of divers then adds £2 per head. Collects this amount from each diver then gives club £2 per diver.

… Garage the RIB

Once the RIB is back home, the engines need flushing with fresh water. Best way is to pump and prime both carbs and disconnect fuel lines. Attach "ear muffs" to engine water intake just above props and feed with fresh water from hose. Once water running, start engine and immediately check tell-tale has water coming out. If not, stop engine instantly and find out why. If is, leave engines running until carbs run out of fuel and engine stops. Repeat with any other engines. Hose down the RIB inside and out, and flush plenty of water round trailer - especially wheels and brake drums. Cover with tarpaulin and secure boat.

Copyright © 2007 Chippenham Diving Club - BSAC1622