This is a diehard diver, maybe he's not sure of his dive tables, so a little extra won't hurt.
Scuba Diving Nitrox - Great for Hangovers and you get to use that Damn Algebra!
Safety, skills and more bottom time - Using Nitrox diving.
Nitrox diving is becoming more popular with divers everywhere -- find out why here! http://aquaviews.net/scuba-guides/benefits-diving-nitrox/
Practical Guide to Nitrox Diving | Scuba Diving
Ice Diving Canada http://www.deepbluediving.org/nitrox-guide/
The PADI Enriched Air Nitrox course will teach you Nitrox diving techniques related to enriched air while diving at the Similan islands or Khao Lak.
Folding Scuba Fins
All you need is nitrox and a regulator
A bag for your Scuba gear