Dolphin swim is what you get at any other port of call with one of these adventures. They do a nice job, you get to interact with the dolphins, which can be cool...but do expect to spend $$ on photos if you want any. That's where they really make their money and where we got a bit angry--after the cost of the excursion, etc, you'd think they'd throw in, like one photo??? Nope.
Haven't done zip lines in Tortola. Went to baths on Virgin Gorda instead this last cruise.