Dive Profiles - Wrecks / Saw Tooth Profiles

[The Kraken]

I thought I should put this in the technical section, but then I thought that, yes, this applies to a large number of recreational divers who dive infrequently, so, therefore, I'm posting it here.

We read a great deal about avoiding "saw tooth" profile dives.

However, often times on a recreational "wreck" dive, the diver may want to explore the outside of the vessel, then the inside and so forth.

Let us suppose that the bottom of the vessel lies on the sand at 90 FSW. The vessel has open hold spaces accessible from the deck area with no overhead structures that would prevent an immediate ascent. The deck area is 20 feet shallower than the bottom. The interior of the vessel can be viewed from within by descending down into the holds.

Should the diver survey the outside, move up, over the gunwale, and down into the hold to continue the survey, or survey from the outside or inside only?

Or does the nature of the survey fall outside of what is considered a "saw tooth" dive profile?

 

[pt40fathoms]

What you describe is in fact very common, however you have to take into account the depth of the wreck before being concerned about a "saw tooth" dive profile.

At 90 feet, a rise to 70 feet realizes a relatively minor decrease in pressure Taking into account the fact that you would be rising to 70 feet, and then descending back to about 90 feet in a slow manner, the risks you face will be nearly non-existent. If you were to use a scooter and ride it like a roller coaster, then I would be very concerned.

If the wreck were shallow, lets say 40 feet, and the deck were at 15 feet, then I would plan the dive a little more carefully if it were an extended dive. The pressure differential at the shallower depth will be much greater, and even though you are shallower, this will have a greater effect on you. Nitrogen loading will naturally be much less at 40 feet, but your bottom times will also be much higher, so the slower theoretical tissue compartments will be the ones most effected.

The most basic rule is GO SLOW in diving. You should not be in a hurry. Think of it as a very leisurely stroll through a flower garden, and for the guys, an afternoon stroll though an antique car museum. Avoid a saw tooth profile, and when you do move up then back down, just go slow.

 

[ScubaDadMiami]

I'd echo 40Fathoms. If you can plan on doing the deeper portion first and then move up, that is best. If you can't, is usually not a big deal unless you are near the limits of your profile and you are then ascending and descending enough to consider the effects on your deco obligation. Never ascend more than 30 fpm when you do have to ascend, use some common sense, and you should be okay.