Techniques for boat diving without surface support

[Still Kicking]

I believe that on my Zodiac I have >= 10ft of 5/16"... more would be nice, but the anchor locker is not large. Due to the very limited conditions in which I will anchor without surface support, I never see the chain lift from the bottom. If I was really concerned, I might put a weight further up the the anchor line to act as a snubber and to increase the incident angle of the rode, but I likely wouldn't be diving in such conditions anyhow.

I've debated this with myself once or twice and value your advice. In the scenario where I don't ascend from the anchor and surface without enough gas to dive the anchor (neither of which has ever happened), I'd rather just drop the anchor line than have the boat float away. For what it's worth, I do try to consider the anchor's ability to release when pulled vertical.

That sounds like a good chain for your boat. Inflatables are light and low profile -- it's not going to exert much lift even in a moderate wind. Also, that's a good idea on the extra weight on the anchor line -- it's called a kellet weight (a weight belt could be used in a pinch). I've never needed one but, like you, I only go out in benign conditions.

As for setting the anchor, if you are able to raise it when you are directly over it, you should be fine. Some people like to shackle the anchor chain to the crown and secure the chain to the ring with a breakaway connection (eg. zip ties) so they can retrieve a fouled anchor. I am not a fan of that because if the boat swings and the anchor gets stuck, the breakaway can fail and you effectively have no anchor. I have thought about adding a floating trip line to the crown so I can pick it up that way if needed but it's a complicated approach that I have never used.

For the last few years, I have been using a longer, heavier chain and mostly anchoring in sand just outside the reef or wreck. The Bruce anchor buries itself pretty quickly if there's a load on it and the heavy chain keeps it set firmly. Raising an anchor from sand all but eliminates the possibility of a fouled anchor and it's much easier to retrieve when running the boat solo.

As for leaving a fouled anchor -- you should have a second anchor onboard if you decide to do that. If you lose engine power near shore you'll have no way of stopping drift without an anchor.

 

[Celt]

I don’t really worry about my anchor dragging when I leave my boat as I use enough weight and scope when shallow. Anchoring in deep water is not so easy, so I tie it in and always use a strobe and reel. I actually worry more about someone coming on my empty boat. I have a large sign that says diver below which I tie to the anchor rope but it doesn’t stop me worrying, you just never know what someone might do when they encounter an empty boat.

 

[rjack321]

Depends on the site, I've done perhaps 400 untended boat dives off my RIB. Another trick you can use/consider is to set a shot line on your target, anchor inshore in shallow water, scooter out to the shot line and drop. Do your dive then scooter upslope back to the vicinity of your anchor and do your safety stops. Surface and surface scooter back to the boat.

 

[Angelo Farina]

Whilst when young in some occasions I did dive from a boat leaving no one aboard, I always did this from a 10-meters rigid boat with cabin, securely locked to the bottom with a long heavy chain and a 50-kg heavy anchor.
The rule of thumb was to unroll a length of chain at least 3 times longer than the depth.
I also owned a Zodiac, namely a MK3-Futura, which I suppose is the same model you have, being roughly 5.5m long, which approximates 16ft.
A Zodiac is a very light boat, due to its inflatable keel.
This is quite peculiar to Zodiacs, making them quite different from modern Rigid Inflatable Boats (RIBs), with their heavy fiberglass body.
This makes an empty Zodiac a very light boat, very easily stormed by wind, and very difficult to anchor properly.
Usually on a Zodiac one employs a small foldable anchor, with a nylon rope (no chain).
Even if locking the anchor in a hole between rocks, such a setup is quite easily overcome by wind and sea.
In conclusion, I never risked diving from my Zodiac Mk3 Futura leaving no one aboard.
We typically were in 4 on the Zodiac, diving two first, two later.
I really do not see how to make a 100% safe anchoring of a Zodiac...
It is too large and too light for hoping to find it again where you left it!
Perhaps with a RIB instead of a Zodiac it could be feasible, but I never owned a RIB.

 

[Still Kicking]

Whilst when young in some occasions I did dive from a boat leaving no one aboard, I always did this from a 10-meters rigid boat with cabin, securely locked to the bottom with a long heavy chain and a 50-kg heavy anchor.
The rule of thumb was to unroll a length of chain at least 3 times longer than the depth.
I also owned a Zodiac, namely a MK3-Futura, which I suppose is the same model you have, being roughly 5.5m long, which approximates 16ft.
A Zodiac is a very light boat, due to its inflatable keel.
This is quite peculiar to Zodiacs, making them quite different from modern Rigid Inflatable Boats (RIBs), with their heavy fiberglass body.
This makes an empty Zodiac a very light boat, very easily stormed by wind, and very difficult to anchor properly.
Usually on a Zodiac one employs a small foldable anchor, with a nylon rope (no chain).
Even if locking the anchor in a hole between rocks, such a setup is quite easily overcome by wind and sea.
In conclusion, I never risked diving from my Zodiac Mk3 Futura leaving no one aboard.
We typically were in 4 on the Zodiac, diving two first, two later.
I really do not see how to make a 100% safe anchoring of a Zodiac...
It is too large and too light for hoping to find it again where you left it!
Perhaps with a RIB instead of a Zodiac it could be feasible, but I never owned a RIB.

Having dived off a 15' Avon with an inflatable keel for 20 years in a variety of conditions, i have to disagree with you.

Set up correctly with a chain and good, non folding anchor (flukes can fail to open on a folding anchor) they make excellent dive platforms and will stay put if you know what you're doing.

You may never have done it, but it can be done safely.

 

[OTF]

I recommend redundant bilge pumps, properly wired and plumbed, with reliable charged batteries. I once came up from a dive to find our 17 foot skiff sinking to the point that the engine was almost under. In very cold water with increasing breeze and waves blowing away from shore.

Or more generally, the boat must be in a condition of tip top seaworthyness. Nothing sketchy. Because anything sketchy will fail at the worst time.

 

[Still Kicking]

I recommend redundant bilge pumps, properly wired and plumbed, with reliable charged batteries. I once came up from a dive to find our 17 foot skiff sinking to the point that the engine was almost under. In very cold water with increasing breeze and waves blowing away from shore.

Or more generally, the boat must be in a condition of tip top seaworthyness. Nothing sketchy. Because anything sketchy will fail at the worst time.

One of the nice things about an inflatable is you have an incredible amount of buoyancy in the tubes. You can fill the boat with water and, unless you have a massive failure on the tubes, it will still float and self bail if you can make headway (don't ask how i know this lol).

I completely agree about things going wrong at the worst time -- Murphy never misses an opportunity on that score!

 

[Joneill]

Extremely bad idea

Agreed - but I’d actually call it extremely stupid!

 

[Still Kicking]

Agreed - but I’d actually call it extremely stupid!

Better to think it extremely stupid and stay safe than to engage in it unprepared.

 

[lowwall]

I'm trying to figure out whether this thread is an example of normalization of deviance or some lesser known behavioral safety lapse.

I think we should start with a blanket statement, "This is neither recommended nor safe. However if you choose to do it anyway, here's how to decrease the risks. Somewhat."