fishb0y:Why can you not touch things (besides fire coral and such) under water? How would interacting with the environment in such a simple way affect it? What about dry land? Does this mean we can no longer touch trees? Not trying to start a fire here, but I have always heard this but I can never see why.
Many corals are covered by a thin layer of mucous that protects them. When you touch you remove that mucous and the polyps underneath die. I have often seen "handprints" of dead areas where the coral has been touched by divers.
We are aliens in the underwater environment and so should try to dive with the minimum impact on that environment. Touching anything has an impact and should be very strongly discouraged.
Some countries have banned the use of dive gloves to protect their reefs. This is an excellent move, more should implement such a ban. With the exception of cold water diving and wrecks.