Another reason why this is a Caribbean Reef Shark. Silkies stay on the move.So I guess there is a steady current there, which the sharks enjoy so they don't have to keep moving to flush their gills as some species do? It's interesting how some congregate at certain stations, for cleaning or whatever reasons. I'll be looking forward to more info...?
" They have been documented resting motionless on the sea bottom or inside caves, unusual behavior for an active-swimming shark. "
http://en.wikipedia.org/wiki/Caribbean_reef_shark