Deepest dive first……. Really?
We are all taught that you need to do your deepest dive first and make your subsequent dives shallower. That is simply safe diving protocol and we all adhere to that… but why? Why does diving deeper on your second dive increase the risk of decompression problems?
It doesn’t, at least not according to Master Bunny Phil
“It’s called ‘Reverse Profiling’ when your first dive is shallower than your next dive and is generally frowned upon by most divers and I think all dive agencies but the reasoning is wrong.
“If you actually look at why this thought process has come about it is to do with maximum dive times, not decompression limits or dive safety”
Whilst controversial it appears Phil has a point but as much as we love him we thought we should look to the Divers Alert Network (DAN) for a bit of guidance.
In their article entitled Reverse Profiling they concluded:
1) Historically neither the US Navy nor the commercial sector have prohibited reverse dive profiles
2) Reverse dive profiles are being performed in recreational, scientific, commercial and military diving
3) The prohibition of reverse dive profiles by recreational training organizations cannot be traced to any definite experience that indicates and increased risk of DCS
4) No convincing evidence was presented that reverse dive profiles within the no-decompression limits lead to a measurable increase in the risk of DCS
"We find no reason for the diving community to prohibit reverse dive profiles for no-decompression dives less than 40 msw (130 fsw) and depth differentials less than 12 msw(40fsw)."
In simpler words, if diving is performed within the no-d limits and the different dives are done within a maximum difference of 12 meters, the current evidence does not show any demonstrable increase in risk of DCI.” All good then….
But what does this mean for the Bunny dropping into the water?
Phil continued (having done that weird ‘I win’ hand stirring dance):“In truth the jury is well and truly out.
What DAN are referring to is research done by the Smithsonian Institute and it did not recommend that divers don’t do their deepest dive first, just that there was no evidence that it presented a problem – it did say that you need to keep the second dive within 12 meters of you first dive”And as ever, you need to stay within your decompression limits on both dives.
Well thanks for that Phil – all nicely cleared up…. not….
Our advice – have a look at this article by DAN and make your own call.