What's your preference for deeper dives? Trimix or Heliox? And how do you avoid the helium squeaks? Some sort of gadget on your radio?
Ah, mate, you’re talking my kind of playground! Personally, I’m more of a Trimix guy for most deep dives but it totally depends.
For example, at 60 metres, I’m using 21/35 Trimix. That means 21% oxygen, 35% helium, and the rest nitrogen. Keeps your oxygen low enough to avoid toxicity at depth, cuts down nitrogen narcosis, and helium makes breathing easier. If I’m pushing past 90 meters, we’re talking 18/45 or even 15/55. Oxygen drops, helium climbs, nitrogen drops off almost entirely. At that depth, narcosis from nitrogen would be brutal if we didn’t swap it out, so in comes your Heliox.
So Trimix, for your average dive, is safer, it’s more forgiving, and you don’t feel like your head’s going to explode when you hit fifty meters. If I’m having to swim someone through a decompression, I use Trimix for them too as much as I can. It’s a little kinder on someone who isn’t used to how it feels to deep dive. Heliox can make your dive tables a nightmare if you’re not careful too, because you off gas so differently. Helium diffuses in and out of tissues a lot more quickly than nitrogen, your muscles hang on to it for longer than other parts of your body, and you need to know what you’re doing or you’re going to be in big trouble very quickly.
But Four is capable of providing all, so it makes my life a lot easier. She can blend based on depth, she can switch without my input if I’m working off the umbilical on an EVA, and she keeps an eye on my tissue saturation for me through my suit. My deep water exo-suit also has both options and blends (remotely from Four) although obviously it’s got a more limited supply. Four’s also got an onboard decompression chamber so if we’re in real trouble, we can bail to her and stave off the bends.
As for the helium squeaks on the radio - yeah, that chipmunk voice is a classic. I stick to full-face mask mics with a built-in scrambler, means the electronics do all the heavy lifting. Otherwise, you sound like Alvin and the Chipmunks under the sea, and nobody wants that during a tricky salvage or rescue. You can also speak a bit slower and deeper, but the scrambler’s your best friend.
@starman-john-tracy still enjoys switching the scrambler off from time to time when it’s just between us. He pretends it’s a comms issue but I know he and @ilikebigshipsandicannotlie just think Gordo four octaves up is funny 🙂↔️