First time without an instructor?

[MXGratefulDiver]

P.S. Bob I do realize that oxygen is toxic at depth . So that nitrox has m.o.d.s based on its percentage. I believe the maximum depth for the lowest mix is 160'. Below that my limited understanding is one would go to heli-ox? and or TRI-MIX?Is this correct albeit a very broad and general explanation?

Basically, yes. It's not something you want to learn about on the Internet ... or even just by reading a book. Take the class ... sounds like you enjoy learning and asking questions and you'll have the opportunities. If you're going deep then you'll want to learn about diving with other gasses that have helium mixed in with them. You'll learn that in advanced nitrox or triox class ... but you gotta get the basics of nitrox down first.

I know what you are feeling underwater ... I've only been diving about 3 years, and am closing in on my 800th dive (in the next week or so) ... didn't realize that nitrogen could be so addictive ...

... Bob (Grateful Diver)