We visited Margarita last November for 1 day as one of the ports of call on a cruise. We chose this island to swim with dolphins as it was the cheapest of all the islands we called at (about £75 each) so booked the excursion via the Ocean Village desk.
We were a little disapointed to find the dolphins in an inland concrete tank, we weren't aware of being close to the sea, so there was no hint of a natural environment for the dolphins. In fact I've no idea where we were geographically * see below.
You need to be aware you are totally dependent on their poolside photographer for any photos of your experience, as the logistics mean that you leave your belongings (including your camcorder) in a changing area away from the activities.
In our case it means that we were held to ransom for the photos, since under normal circumstances you are supposed to be shown all the pictures of all your party (meaning the entire coachload - all in the pool at the same time !). Then you would naturally wish to choose only the pictures of your family and friends for purchase. Since it was late in the day and we didn't want to miss or boat sailing there was no time for this so it was a case of "Buy this $30 CD with ALL the pictures on (95% of them of strangers), or go home empty handed". The entire coach party was up in arms over this ! In the end only one or two of us bought the CD and we had to haggle with Ocean Villages Photography shop to provide pictures for everybody from these CD's. It was difficult and they didn't really want to help.
Thank good ness for the dolphins, at least you could trust them, they were wonderful, friendly and performed all their tricks as good as gold. Whilst we did enjoy the experience, in hindsight I would have chosen somewhere else for our first experience of swimming with dolphins.
Edit :- * We went to Waterland Mundo marino (it said so on the CD label)