Any downside to extending the safety stop?

Assuming that you have no issue with getting low on gas, that you won't be separated from your buddy or dive group, and so forth, is there any disadvantage from a DCI perspective to extending the safety stop at 15 feet from 3 minutes to a longer period?

Will going from 3 minutes to 5 minutes or 8 minutes, say, make any meaningful reduction in residual nitrogen?

Thanks in advance.

There is NO disadvantage in adding time to a safety stop. I am having trouble finding it but DAN did a report that 5 minutes is a good time because it takes about 5 minutes for your blood to be circulated though your body, this causes much more offgasing than a 3 minute stop. I honestly don't see a reason however to extend a "safety stop" to 8 minutes. I commonly hang out at 20 for 2 and 10 for 3, with about a 30 second transition from 20-10 and 10 to surface. Above around 30 feet your body stops on gassing significant amounts of nitrogen.

In warm-water-pretty-fish dives, by being clipped off and motionless ay 15fsw, I have seen the most amazing things swim (and float) on by. It hasn't killed me yet.

I have hung under liveaboards for 35+ minutes and watched what was the largest Barracuda I have seen in 55 years, I have been bathed in millions of floating linked Salps and Venuse Sea Girdles, big Rays coming by for a look-see, Sharks, and much more.

If this behavior is going to kill me, well- it hasn't yet so far, and whatever... it has been well worth it!

Additionally to what GCullen94 wrote, more can be better, but only if:
- you can stay always at the same depth, or else you'll have your ears 'clicking' all the time and this can lead to equalization problems later (mind that you'll feel the pressure variation is higher on shallower depths);
- like Doc said, on warm-water-pretty-fish dives, is perfect to see great stuff. One day I was diving quite deep in Maldives looking for sharks and saw one or two... the guys with a PADI Open-Water certification only, diving close to the top, saw mantas, barracudas and guess what... a lot of sharks.
- you're comfortable with your temperature

It can be worst if:
- you're low on air
- strong currents and nowhere to grab a hand to stay quiet
- your dive-buddy doesn't know you'll stay more time than the expected
- you did a bad profiled dive and think this extended stop will save your bad planning*

* how to avoid it? always plan your dive. And if it really happens? Warn the dive crew and get oxygen, but please review your diving books before going to dive if you're not sure how to handle urgency situations like these!

Do it all the time. As noted it is amazing what comes cruising by.

On most dives, we try to be first in the water and last back in the boat. While the others are scrambling for the ladder, I like to hang at 20 feet and look for things under me. I'd much rather be down than on the surface or at 10 feet with people behind and in front of me lining up for the ladder.

Many guided dives at resorts and some liveaboards will begin deep but end with the group floating around a shallow (10-20 feet) coral head for as long as one's air holds out. I've ended dives like that with a good 20 minutes of bobbing around a coral head, "watching the pretty fishes go by," as they say.

I read the DAN report also - but haven't kept a copy. I frequently shore dive and will often spend 20 minutes or more in the shallows around 2-3 metres before surfacing to exit and it has never done any harm.

According to my log book my longest dive on a single tank is 1 hour 49 minutes and I didn't get over 3 metres for the last hour of the dive, with a maximum depth of 10 metres. This was a night time shore dive and was great for watching things bimble past - Phil.

Phil

No, there is no real downside. A safety stop is essentially a nonobligatory decompression stop. Extending it allows more time for you to off-gas nitrogen. So assuming you have the backgas permit the stop, and the boat isn't leaving without you, you are, in fact, reducing the chance of DCS.

When I was diving NC in 2010 we had great vis for most of the dives. I'd hang until I was down to 500psi. Oh yeah never know what might swim by. I kinda envy the RB'ers they can do their entire SI at 15' and then begin the 2nd dive!