I bascially agree with this (and similar posts).... HOWEVER: A gentle touch or stroke as a sea creature passes you is one thing..... a GRAB AND RIDE is an entirely different beast.
If you are not sure if your interaction with the "critter" has the potential for harm, just look.
Sea turtles: We have lots of them here at my favorite dive site in Hilo... I'll often see over a dozen very large turtles every dive. They are friendly, will often come up to divers, and are fun to
watch. The reason they are so plentiful and "tame" is that we follow a "look but do not touch" rule (and they are protected by law here, at least as far as hunting goes).
I do not think a gentle touch or stroke of their shell would bother them... but I still refrain.
Grab a turtle? No.
Ride one? Absolutley Not.
Best wishes.