I did a lot of SCUBA when I lived on Pensacola Beach including a lot of beach diving and cave diving. I had one tank set up specifically for cave diving with a reversed reserve valve. I helped a local dive instructor with training for new divers. I got no pay but was not charged anything for the boat trips. All instruction was off his Boston Whaler. He knew where all the wrecks were and we used his LORAN and fish finder to locate them. I would demonstrate buddy breathing, help track dive times, show them how to dive off the boat without banging their head on the tank, demonstrated decompression stops, and verified that the air was turned on before they dived. Then I got a 6 month work assignment to Pago Pago, American Samoa and decided to take my SCUBA equipment. I joined the dive club there which was nothing more that a cost-sharing arrangement for a SCUBA compressor located at the airport. Members were given a key and just filled up their tanks whenever they wanted. Great visibility of over 100 feet and lots of giant tuna to see.