In our training, we were definately taught that touching, never mind
riding sea life is a no-no. In our limited experience (86 dives) we have seen a variety of divers including especially DM's stretch that rule to greater and lesser degrees.
We have been with DM's who picked up certain creatures to show them to divers (sea cucumbers, shrimp, octopi, yellow line arrow crabs). In some cases this seemed very much OK to us, in others it seemed a bit intrusive. We've also observed other divers doing the same thing, including "repositioning" of sea life for the purpose of photography (I can recall this relating to seahorses, hermit crabs, and octopi). We have avoided following their example and don't touch - if we can't get a good shot of X animal, we will look for another. Please don't misunderstand, the majority of the DM's we have encountered touch nothing, and clearly guide divers not to (especially when it comes to whale sharks, mantas and sea turtles). "It depends" seems the best answer; and good judgement as to when this is OK must be employed. We have erred on the side of caution and don't touch.
In Little Cayman, we were told not to touch anything
"other than the Nassua grouper, because they touch you first." IMHO, while the Nassua grouper certainly follow divers and rub against them / bump them, the practice we observed of divers then gently petting them or rubbing under their chins is not wise, and may lead to problems. We feel this may have been a factor in a bizarre experience we had when a grouper, odd as this may seem, repeatedly attacked my daughter / dive buddy. While not a dangerous situation in and of itself (very small teeth
), this could have led to panic in a truly inexperienced or jumpy diver - and
that could be serious. If interested, please check out my post on the incident.
http://www.scubaboard.com/forums/near-misses-lessons-learned/349261-grouper-attack.html