My son lives on Raft Island. He is PADI certified. He is asking me about a small tank that he can use in front of his home and look under his boat. He does not want a large tank and is interested in a tank that may give him 20+ minutes of air. I am also certified and may find the same useful. Not a safety or back-up tank but a light easy to carry tank for very short shallow dives. Garry
Aluminum tanks are cost efficient, long lasting, and readily available, which is why they are easily the most common scuba diving tanks in the world. Lighter than steel tanks, aluminum dive tanks are easier to transport and swim with, giving your shoulders and arms a break on long treks.
Because of their light weight, some aluminum tanks will begin to float at the end of a dive, once the oxygen supply is nearly depleted. To combat this, it's common to counter-weight an aluminum dive tank with approximately 4 pounds. However, 'Compact Neutral' aluminum tanks are made with thicker walls, which increase the weight and help to counteract the positive buoyancy problems at the end of a long dive.