Trim... the old & the new

[Rick Murchison]

Not many years ago, divers were taught that the optimum swimming position on scuba (trim) was about ten degrees head up from the horizontal, using a slow, wide flutter kick. If you were trained more than two or three years ago, this is the way you were probably taught to swim underwater.
Well, it turns out that this technique sends downbursts of water as much as ten feet below the diver, where they can stir up silt, decreasing visibility and covering living organisms with a blanket of suffocating debris. Usually animals can brush this silt off without any harm, but it wastes their energy, and sometimes it can actually smother delicate polyps, larvae and other small sessile critters.
Now we know that we need to swim in a way that directs the disturbed water behind and above us to avoid these potentially damaging downbursts. To do this we take a page from the cave diver's book, trimming for a slightly head down rather than head up position, and using either a modified flutter (a shorter stroke kept above the body's extended centerline by keeping the knees slightly bent) or a modified frog kick (again, the kick is kept above the extended body centerline by keeping the knees bent).
If you haven't yet tried these new swimming techniques, I invite you to give them a try - look behind you and see the bottom isn't getting stirred up by your finning.
Rick

 

[d33ps1x]

Looking forward to using my new jets and techniques and helping not to stress out the reefs this January.

 

[DORSETBOY]

Frog kick's deff the way to go! and not just for satisfying the 2nd most important rule of scuba diving, to look cool!
It's interesting that when diving in caves we say that people should use a bicycle kick and yet when in ow around a reef for example we're supposed to expect students to use the standard straight stiff leg look!

 

[MikeFerrara]

Good post Rick

 

[Rick Murchison]

Frog kick's deff the way to go! and not just for satisfying the 2nd most important rule of scuba diving, to look cool!
It's interesting that when diving in caves we say that people should use a bicycle kick and yet when in ow around a reef for example we're supposed to expect students to use the standard straight stiff leg look!

The modified flutter and the bicycle kick may look similar to the casual observer but they are different things entirely. While the bicycle kick is ineffective and inefficient, the modified flutter is both effective and efficient. Takes a little practice, though.
Rick

 

[archman]

I almost always use the frog kick too, but I usually keep my head slightly up. It's not because I was trained this way (my OW instructor simply told us to "stay down"), but for increased forward (and upward) field of view, and to expedite communication with my students and/or survey teams. Also unlike the cavers, I'm constantly twisting around to check my divers and talk to them, and the slight head-up is better for this, unless you're upside down (and let me tell ya', upside-down hand signals are no picnic).

I try to instruct all my divers to frog kick as much as possible, and (gasp!) use their HANDS rather than feet to help maintain stationary positions when near the bottom. If they're hovering closer than 2-4 meters off the bottom, I discourage from kicking altogether (after all 99% of divers hover vertically & head-up). In all the reef courses I've taught, the only common cause of siltation has been from divers kicking up when stationary (not counting direct sediment contact).

The only times I go for the head-down angle are when I'm hugging the bottom (<.5m clearance). However, I don't normally do this when there's sensitive biota underneath.

 

[MikeFerrara]

Just a suggestion...

If buddy teams are at the same depth you can see eachother and communicate just fine without going head up. You can see in front and in back with a tilt of the head. When a diver gets in your blind (above and behind) spot then you have to do funny things to find em. Tell em not to do that. LOL

Hovering in a horizontal position is a better way to keep from disturbing the bottom that using hands in a vertical position.

 

[divebunnie]

I too use the frog kick, I actually find it a more balanced way of finning than the old individual fin kicks, as well as the obvious benefits to life below me.

 

[archman]

Hovering in a horizontal position is a better way to keep from disturbing the bottom that using hands in a vertical position.

By "hovering" do you mean sitting still, or moving? I find it much more difficult to stay motionless and horizontal, opposed to moving and horizontal. There's some inherent tendency to go vertical (head up or head down), which is exacerbated by fiddling with equipment, and my groups "fiddle" quite a bit and are chatty. Maybe this is a weight belt and center of gravity issue... backplates may be better for horizontal trim.

Very minor peeve.
One more thing that I cannot do when head-down, is keep my mask clear when I have a beard (I don't smear silicon grease on my face like the hardcore people). Head-up the leaking water collects under my nose and is cleared at every few exhales. Head-down the water collects by your eyes. It's a world of difference, and forces me to SHAVE in the winter months when I do solo research dives. I HATE SHAVING.

 

[DA Aquamaster]

I am an avid fan of a modified frog kick and once you develop the leg muscles for it, it is very fast and efficient and an excellent way to avoid stirring up the bottom. I prefer a slightly head down position primarily because most of my diving is in heavily silted bodies of water with limited visibility. Besides it's also a matter of pride to be able to swim 6 inches off a silt bottom and not stir up any silt.

I have also found that when leading a dive that a slightly head down position allows you to go slightly farther head down and then just bend your neck forward to see behind you.

Maintining the postition easily is just a matter of proper trim. In cases where you need to be right down on the bottom, adding a bit of air so as to be a pound or so positive will allow you to in effect power down to the bottom and then to float back off the bottom if you need to without raising any silt.