I personally think every diver should have a pretty good grasp of deco, a feel for when it's going to be necessary and the skill to accomplish an accurate stop without the aid of a rope, float or down-line. However, I realize that's unrealistic in today's world, so my answer to your first question is "no" - I don't think it's "necessary" for the recreational (vacation + a few weekends a year just sightseeing and taking snapshots underwater in benign conditions well within the NDL for fun) diver.Karibelle:Do you feel that deco theory and basic deco procedures are necessary for a recreational diver? (And I'm using PADI's def'n of recreational, in that no dive would be below 130' and that NDLs would not ever be reached.) And could you elaborate a bit on "basic" for me? I need some scope to understand what you're talking about.
kari
Basic would include being able to explain the basic ideas and assumptions behind Haldanean and modern bubble "tension/threshhold" theories, a little background on current research and thinking on the various models in use, their similarities and differences in basic profile structure - nothing complicated, just enough to get a good feel for "reasonability" in dive profile structure and what constitutes a reasonable profile for one or two pressure groups outside the NDL.
Skills wise, the ability to plan and to track gas consumption, navigation, bottom times & depths accurately and to execute stops of at least 10 minutes +/- 1 foot while dealing with simple problems (clearing a mask, retrieving a reg, sharing air, writing a note, etc) would be considered "basic."
Rick
(Edit - P.S.) I might add that in the "old days" we only discussed Haldanean theory, 'cause that's all there was, and we did use lines as aids in making stops, 'cause we didn't have any BCs