Damn, that’s a lot of dives. I only did the first level PADI, but I didn’t even think 270’ was possible with SCUBA gear - what’s your deepest?
I am qualified as a Rescue diver and I used to teach dive classes. I have dove everything from farm pond looking for a wedding ring someone lost(I have an underwater metal detector) to rivers, Lake of the Ozarks, a lot of dive trips to the Caribbean on "bareboat" catamarans and a trip to an island off the coast of South America (Bonaire).
You can do 270 I have a friend who has done 300 But you have to be well trained and you are using Mixed gasses (Trimix). If you look at the pictures of the divers you can see them with all kinds of tanks strapped to each of them. The small tanks are hooked to a "Rebreather" that recycles the air they are breathing you can use that to some depth just below 200ft. When you get deeper you switch to trimix gas, and that consists of compressed air, helium gas, and Nitrogen gas. Breathing compressed air at that depth will kill you.
The deepest I have dove is about 180ft. I'm not into deep diving. Once you get to 200ft and deeper it start to get dangerous.