Diving off small boats -- Questions

[Rick Inman]

Congrats on the boat!!! What fun you will have!

 

[String]

We tried to anchor on the wreck a couple of times, but once the anchor fouled, and the second time we were dragging it, despite adequate scope.

I fail to see why anyone anchors to a wreck, especially for small numbers of divers. To me it just has no advantages at all.
It destroys the wreck, renders the boat unable to rapidly respond to an emergency or other shipping and many other things.

It was decided to create a shot line and shot the wreck. The shot line had a fender at the top for a float. The three divers were dropped on the buoy and went down the line to the wreck.

That's how 100% of all wreck dives are done here and the best option. Or for things like areas with large tidal range or current possibly consider a top-tensioned shot to avoid needing loads of rope.

On ascent, we came up the line, and surfaced at the buoy. Because of the wind, we had some surface current, and it was hard to keep station at the buoy. The boat wasn't far downwind, and my two buddies started to swim to it.

Standard here if you really insist for any reason on coming up a line is once the captain has acknowledged you've been seen you release and drift. This makes the pickup FAR easier for the guy handling the boat and also more comfortable for the divers.

He was trying to position the boat so we could swim downwind to it, and it wouldn't be upwind and drift down onto us.

He should position the boat down-current and you should drift towards him no swimming needed.

If you are ascending the line, is there any point in shooting a bag?

I'd question why you'd ascend a line instead of just coming up a bag given a bag is far more comfortable especially in current.
Also some skippers like it as 1 bag per diver he knows ALL the divers are on the way up.
However doing it on/near a line is just asking for entanglement.

The captain of the boat was worried about a large tug and its towed ship, that appeared to be heading straight for our buoy, but I'm not sure an SMB could have been seen any further than the buoy, nor, by the time it was seen, could the tug have changed course. (The captain contacted them by radio, but by then, it was obvious they were going to miss us.)

Again its a reason for not having an anchored boat. First rule of coxing a dive boat is protect the divers, that means aggressively patrolling the area and if any sort of hazard appears you put your boat in-between the divers and them to make them change course or notice you, you use the VHF, you even use flares if needed.
An anchored boat cant do this safely or in enough time.

Once the divers are on the surface, what is the best thing for them to do? Should they try to make for the boat, or stay with the buoy until the captain okays an attempt to reboard?

Who's in charge, once the divers are on the surface?

Normally i'd say once on the surface its the captain that calls the shots but in this case id seems to me as if he isnt great at his job.
However even though all divers should be alert and ready to immediately redescend if something happens like a high speed jetski or something silly appears.

 

[TSandM]

Or for things like areas with large tidal range or current possibly consider a top-tensioned shot to avoid needing loads of rope.

What's a top-tensioned shot? I would like to make a shot line to keep on the boat, and I've been puzzling about how best to do it.

I see pros and cons to anchoring. Certainly, if you're anchored, the divers have an upline and the boat doesn't have to run its engine while retrieving divers, which is much safer when the boat is small and the engine is an outboard. I'm very wary of props. On the other hand, if the boat is anchored, the divers HAVE to come up the upline, which includes hanging onto it if the current is significant. But at least that line connects the divers to the boat, which, after Sunday's experience, has become an important concept to me.

 

[captain]

Rather than using a fender as a float I have a large inflatable 30" diameter orange commercial fishing buoy. It is a lot more visible than a fender and commercial boats are used to seeing them and won't confuse it with a lost fender. Plus it has a lot more buoyancy and would be harder to get pulled under by divers.

 

[String]

What's a top-tensioned shot? I would like to make a shot line to keep on the boat, and I've been puzzling about how best to do it.

Shot put – how to deploy a shot-line - DIVE Skills & Thrills

Not a great article as no pictures on shot types. Ive got plenty of student notes here but obviously not online. The basics are there anyway.

I see pros and cons to anchoring. Certainly, if you're anchored, the divers have an upline and the boat doesn't have to run its engine while retrieving divers, which is much safer when the boat is small and the engine is an outboard.

Not really. If for some odd reason they insist on an upline then use the shotline (and dont dive in currents). You approach divers nose on into the wind or current so you are always in control and very slowly. Then you switch into neutral for the last few meters and drift onto them. It happens hundreds of times here every single weekend nationwide with no problems. You should NEVER approach divers with an engine in gear regardless of the engine type - however if you're coxing the boat properly you should never need to.

I dislike anchored boats for the reasons above - it cant respond rapidly to diver problems, cant respond at all for surface traffic hazards and means divers have to return to a line which if you missed slack or the tide has turned is difficult or impossible.

For anyone diving off boats or handling dive boats i'd highly recommend reading "Seamanship:- A guide for divers" ISBN 13: 9780953891979

Manuals & Books - BSAC

It covers protocol for drop off and recovery from both skipper and diver point of view as well as tides, weather, rope work, emergencies and other things. A large part of it is tailored for outboard engine/small boat work as that's what most diving here is.

 

[TSandM]

Thank you for those links, String, and for your PM as well.

 

[SkipperJohn]

The OP touches on another point about the dangers of diving in or near commercial shipping lanes. Please don't read this as an attack on the divers, but as a reminder that even if you do everything right there are other dangers out there.



Question- what would you have expected from the tug if it were on a collision course?

At the range that a commercial vessel can spot divers, surface marker bouys, or alpha flags flying on small boats, they are likely to be beyond the point where they can maneuver around them. This is especially true of tugs with tows, which already have severly restricted limited maneuverability.

It isn't a matter of right of way, it a practical matter of collision avoidence. I don't know about divers per se, but lots of pleasure boaters have died from collisions, despite possibly having the right of way, in crowded waters such as Long Island Sound, and other similar inland waterways.

You have to be extra cautious diving near shipping lanes, planning not only to avoid them, but also making sure that wind and current won't drift you into them, lest you put your captain in the difficult position of deciding whether to save his boat or save his divers.

All good points. And consider these additional points. First of all it is technically illegal to anchor in any navigable area except in so designated anchorages (or outside the channel). Second of all you are legally obligated to deploy an "at anchor" marker during the day or the required light at night. Now, this is all seldom done but should there be even a minor mishap then these laws & any violations will be scrutinized.
From a practical point of view, and I can't stress this enough, get a radar reflector! There is a very good chance that your small boat will not show up on a typical radar. It is mostly made of fiberglass and the only chance you have of reflecting radar is your engine which sits too low in the water to be of any value. A radar reflector will make your small boat appear like a huge ship on any radar. It is $80 well spent. I KNOW mine has saved 1 collision for sure (another boater who was recklessly speeding in heavy fog told me he would have hit me but thought to swerve around "that big ship").

 

[fireflock]

Things are handled differently in different parts of the world. Conditions are different, so it makes sense to some extent.

In NC, it is common for the first diver (or team) to physically tie the anchor line into the wreck. More often than not, this means wrapping the chain around a substantial part of the wreckage. Sometimes a mate jumps in with the anchor and rides the anchor down. Sometimes the anchor is dropped on a known spot and the line is kept slack until the divers descend and have a chance to tie in.

The first rule for ascending and descending in NC is 'Don't let go of the anchor line'. The wreck isn't under the boat, there are currents (which can be different in the top, middle, or bottom, of the water column), and conditions topside sometimes make it hard to spot a little diver in a big
ocean.

Anchoring to the wreck also makes logistics easier when dive teams switch places (1 in the water, 1 on the boat).

Sometimes we will drop on a shot line or a free descent, but only on the nicest of days with divers who have substantial experience diving offshore NC.

I know things are not done this way everywhere, but this system has evolved over the years and works well in NC.

Rich

 

[Hank49]

I'm interested in the idea that it's preferable to have the boat upwind and drifting down on the divers. This is what our pilot was specifically trying to avoid. In current, it always seems that the boat tries to be downcurrent from the divers, and let them drift down on it; is it different in wind?

If I understand what you're asking, wind and current will both put the boat down current or wind from the anchor line, which if the divers ascend, will but them upstream from the boat.
If you come up downstream and the boat cuts loose to come get you, I don't worry about my small (25 or even a 40 foot boat) boat drifting down on me. It's not like it's going to kill you. Usually it's drifting bow first and you can come along side of it no problem. (be sure it's in neutral) You're over thinking this small problem.

 

[Darnold9999]

Something to consider is that a tug towing a raft of logs (which is what we see pretty regularly up here) has almost no manuverability at all. They simply can't stop or turn even if they did manage to see a SMB, float or diver. If you are going to dive anywhere where you might be in the way or there is any possibility you might get blown into the way your boat captain must be prepared to tow you out of the path and/or you must be prepared to go back down. If you see a tug bearing down on you - assume that the course the boat is on now will be the course it will be on as it arrives. If you can see him while you are in the water - he is far too close to do anything about you.

A site I would love to dive - nice narrow channel - what looks on the charts to have nice walls and rock gardens, lots of kelp, lots of seals feeding and moderate current has these tugs and rafts regularly transiting just offshore. The conditions will need to be perfect before diving such a site. 0 chance of getting blown into the channel by current or wind and a live boat with an experienced captain to deal with the unexpected.

Re pickup every site is different, if the shore or some hazard is not an issue my pickup routine is to park upwind and just slightly ahead of the group and let the wind bring the stern of the boat to the divers - engines off - I can assist divers at that point. Don't fall in! My dingy on a 30 foot floating line provides a grab point for divers or if I do manage to fall in somehow.

If there is any hazard, shore, shipping etc. at all then back into the divers facing away from the hazard and if at all possible away from the wind - engines on, confirm that the props are not turning and remain at the helm. Divers are responsible for getting back on the boat. You need to be in a position to be able to engage the engines to avoid the hazard without any risk of the prop tangling the shot line or harming a diver. With a small outboard I would probably kill the engine rather than trust it to remain in nuetral while divers were climbing on it.

There is no single answer here - what the captain does will depend on the situation at the time. As a diver I have been asked to swim 300 yards to get to a less risky place for pickup. A very strong partly onshore wind came up while we were down on a recent dive and there was a corner a couple of us could swim to that protected us from wind and waves. Others were too far away to make the swim safely. Pickup for them was a very nasty business with divers trying to swim to stay off shore and the boat backing in to pick them up one at a time on a go go go basis.

The captain is in charge - no discussion - no arguments. Disagree once you are back on the boat and everyone is safe.