Mixed gas on a shallow wreck taught me a lesson I won't forget

I was diving a 90 foot wreck off the coast of San Diego last month, and I decided to run trimix even though the depth was totally within air range. My thinking was that it would keep me sharper and reduce narcosis, and I figured it was a good test for a new gas blend I was trying. But man, I didn't account for how much slower my bottom time would be with all the deco obligations. I ended up spending 30 minutes on stops in 50 degree water, shivering and waiting, while the guys on air were already sipping coffee on the boat. What I learned is that trimix isn't just about depth, it's about planning the whole dive profile, not just the bottom part. Has anyone else tried using a deep gas on a shallow dive and regretted the extra hang time?

3 comments

3 Comments

gracec161mo ago

Jumping in here with something nobody's really touched on yet: running trimix that shallow actually messes with your buoyancy in a way air doesn't. The different gas densities make your wing and drysuit act totally different as you ascend, so you're fighting to stay neutral the whole time on those deco stops. I've seen guys end up doing extra time because they couldn't nail their buoyancy and kept drifting up or down during the hang. Plus, the cold water makes your regs breathe way worse on that blend, which only adds to the shivering misery you described.

vera_johnson91mo ago

30 minutes on stops in 50 degree water" sounds brutal, was the extra deco time worth it just to feel a little less narced on the bottom?

karen3611mo ago

I read somewhere that some of the old-school cave divers actually swore by this kind of mix even for shallow stuff, said it made their heads feel clearer. But yeah, those 30 minute hangs in cold water sound like a special kind of torture to me.