I have solar on my house, avoid single use bottles, keep my thermostat at 56F when I am not home, try to consolidate my driving trips. All of that is important for the environment. Burning $20 worth of gas so I can putter around the sea floor for a couple of hours is not eco friendly. I will open derelict lobster pots and recover lines and pieces of litter, but it is much more about how you live everyday than what you do while diving. Although killing lion fish is a pretty good one.
The best things you can do to improve water quality are at home, like don’t fertilize your lawn, compost food waste. Make sure your car doesn’t leak oil. Recycle papers and plastics. Don’t ever buy bottled water.
Every gallon of gasoline creates 22 lbs of CO2. Average household electricity produces 5-10 tons of CO2 a year. Cut back on meat consumption, methane from cattle is 20 times better at trapping heat in the atmosphere. Changing over to all LED bulbs will do a lot more than picking up junk while diving. The neat thing is, you can do both....