Current is the Worst

[Doc]

For most of the readers (323 so far), I would like to add a comment lest you never dare flop in where there is a current.

•1/4 mile an hour current, you can not swim against. 3 mph and you are tumbling along

•On a dive, go along with the current, but always learn by experimentation with its velocity and flow near the reef, behind rocks, etc- it works like winds over a mountain- just like sailpane pilots utilize. Laminar flow it is called.

•In unknown areas, stay close to your locally experienced DM. I like the ops where the pick-up boat is following his towed marker. Most of these guys can see your bubbles from their level no matter what, but why screw around? If you get separated, from him, stay with a cluster, your bubbles are more easily seen.

•"Downwellings" are truly scary things- but only if you notice them late. Be aware of your surroundings and again- play your distances from the reef walls. A few feet can make a huge difference. If you are really on top of things, I do not believe there is a downwelling that can overwhelm a diver (or at least in a place where those not superbly trained were likely to venture). I have not seen such a thing.

•If you do get separated, use your own best judgement as to when to abort. You had better be absolutely certain as to how to deploy your sausage/SMB from depth, allowing 25' of line to safely pay out- while you remain at depth. You will hang there, then at 15fsw, calmly, while the pick up boat locates you. It would be real smart if your driver had seen your SMB and its particular marks- that way he will know it's you and not some other boat's problem child.

Mastery of surface signaling is essential, and this doesn't mean that you do this at the surface. Learn the skills, ask questions, practice, advance.

 

[dave4868]

For most of the readers (323 so far), I would like to add a comment lest you never dare flop in where there is a current.

1/4 mile an hour current, you can not swim against. 3 mph and you are tumbling along

All great advice!

I find it useful to estimate current in inches per second and then calculate the mph or knots. Then it hits home how limited is my ability to swim against current.

1 mph is approximately 18 inches per second. 1 knot is approximately 20 inches per second.

I think you are pretty close with your statement that 1/4 mph current is something divers cannot swim against, at least not for long....

Dave C

 

[Ardy]

Roatanman - great advice particularly the "It would be real smart if your driver had seen your SMB and its particular marks" never thought of this before excellent idea.

The down current that killed the guys in NZ is now well known. It comes over a large rock platform and falls into deep water and can drag even very fit divers down to 80-90m (260-295ft) this is serious stuff. As you say there aint a lot of these around thank goodness.

 

[Ardy]

All great advice!

I find it useful to estimate current in inches per second and then calculate the mph or knots. Then it hits home how limited is my ability to swim against current.

1 mph is approximately 18 inches per second. 1 knot is approximately 20 inches per second.

I think you are pretty close with your statement that 1/4 mph current is something divers cannot swim against, at least not for long....

Dave C

Dave it is amazing how little is needed to stop a diver in their tracks. I dived in Fiji a long time ago in a hole in the coral called the Blue Hole. It was the end of slack tide and I enjoyed the dive. Trying to get out of the hole against 18" of water coming into it from the coral platform was nearly impossible and I was dangerously fit in those days.

 

[Tassie_Rohan]

All good points - but I'll add the key event in many 'missing diver' events:


Surface when they tell you to.


No matter how much air you have left, and regardless of how experienced a diver you are, if it’s a 40 minute dive be on the surface at 40 minutes: the boat will be on the look out for you.

Again and again I hear of divers who separate from the main group and then decide to stay down well past the allotted time, without a smb deployed. They surface 10-20 minutes later to find themselves well away from the pick up boat, if they can see it at all.

Being able to shoot a SMB from depth is also a very useful skill to have in such condtions.

Cheers,
Rohan.

 

[Tassie_Rohan]

There were 4 or 5 Kiwi's killed a few years ago when they were dragged down to 80-90m before the current let them go, only one of them survived. Scares the bejesus out of me that sort of thing.

I assume you're taling about the french pass accident - looks like there was a was a long, long chain of errors.

Here's where they were diving - the current runs at 2 metres a second, and it looks like a waterfall: definitely isn't the best place to send hungover trainee 'zero to hero' divers...

Some times its just best to thumb the dive. New divers often don't have the experience to make that call: but in the case of French Pass I can't beleive anyone would get into the water.

Cheers,
Rohan.

 

[lemon]

OMG. :shocked2:

 

[TheBigPhillyFish]

So seeing that most of the reply's in this post are way more experienced then I. What would the proper procedures be for a downdraft current, and a updraft current? I would only assume, control your decent/accent would be your primary concern.

I would like to know! I have been lucky not to have experienced this occurence, but I would like to be prepared in the event it ever does occur.

Thanks!

 

[dumpsterDiver]

A number of years ago I went for vacation to the Seattle area and ended up in the San Juan Island area and decided to rent a tank and go for a shore dive. The darn dive shop never even mentioned about tides and I was too stupid to ask. Went off some rocks for a solo shore dive and needed to exit close to where I went in.

Man, they have some currents up there! Don't even remember how far out I got, but really had to crawl and fight my way back in as the current picked up fast. It was one of those dives that I pulled off with muscle rather than experience or brains. I had no surface support and I barely made it back.

When I was turning the tank back in, I think I remember asking about currents and they said it can run like 7 kts or something there. Sometimes local knowledge is very important.

 

[Tassie_Rohan]

TBPF>>>>>>>>>
What would the proper procedures be for a downdraft current, and a updraft current? <<<<<<<<<<<<


Watch you depth gauge frequently during current dives - 90% of divers who get caught seem to be blissfully unaware that their depth has changed: They are too busy enjoying the ride and watching the world go by to realise that they are now at 40 metres and dropping....

Watch ahead of you - if the fish are pointing up or down and swimming to stay in place then you have an up or down current. Schools of fish often gather as up currents bring goodies from the depths...

Watch the topography ahead: up- and down-currents often occcur when the current you are riding passes over a rise or a drop off.

Get ready to add or vent air if you see it coming. Add or vent only a little bit to start off with.

Notify you buddy and get close to them - else they are going for a trip without you.

If you get caught in a strong downcurrent get close to the wall - the current is a lot less within 1-2 metres of the bottom/wall. Add some air to help you ascend - it can be exhausting to kick against a strong down current - but be be prepared to vent your air as you ascend and the current releases you closer to the surface.

Cheers,
Rohan.