On Thursday, October 3, 2019 at 8:49:06 PM UTC-4, Dan Marotta wrote:
I've never heard of a dive shop supplying oxygen.Â* During my scuba
training in the early 60s, I was taught that oxygen is toxic at high
ambient pressure as below some depth which I didn't bother to research.Â*
Imagine filling a scuba tank (dive bottle) with oxygen and killing the
diver!

Divers keep a bottle of O2 around in the boat to treat bends or just to get rid of nitrogen in blood faster to be able to dive more in a day.