Gotta-Have Gear: Two of anything that keeps you alive. In recreational diving the surface is an accessible haven no more than 130 feet away. Not so in tec diving. Standard tec gear must include at least two separate regulators, buoyancy systems, computers and/or depth gauges and timers, cutting devices, etc. Cave divers carry at least three lights each. BCDs have separate bladders and harnesses, and they must have adjustable D-rings and a crotch strap.
Plus Gear: Multigas dive computer. Tec divers use enriched air nitrox, trimix (oxygen, helium and nitrogen) and oxygen for deep diving. At one time, these kinds of dives were only possible with special tables, but today leading dive computers allow you to program them with different gases. Also, eighty-six the pocket pouch on your BCD harness it gets in the way. A better option is a thigh pocket on either or both legs of your exposure suit.
Gotta-Have Non-Diving Accessory: Laptop computer with decompression software. The days of using preprinted tables for tec diving are gone. Today's tec diver plans a dive with software that calculates decompression, gas use and oxygen exposure, then generates backup tables. Yes, you need this even if you have a multigas computer, because you still have to plan the dive.
Gotta-Have Movie: The Abyss (director's cut DVD with all the special features), starring Ed Harris. The ultimate underwater adventure carried off with the detail demanded by James Cameron, technology and gadgets star just as much as the excellent cast. The story of the making of the movie, much of which Cameron shot underwater reel-for-reel, is as dramatic as the plot itself maybe more so.
Gotta-Have Book: Fatal Depth by Joe Haberstroh. This book covers the often-tragic history of tec diving on the wreck of the Andrea Doria. It is a grim reminder that tec diving can be dangerous and that divers who choose to dive beyond their abilities or disregard procedures have an unfortunate tendency not to come back alive.
