Hi Susie,
We went to Ocean world on our visit to the Dom Rep back in Feb/March, it does have its own website which gives you a full tour and guidance as to what is there...you can find it a this link
http://www.oceanworld.net Myself and my 4 year old son went, taken by coach from our hotel we arrived about 915am before the first of the encounters had started for the day. because of this they announced buy one get one free offers on the shark/sting ray encounters which were $45 each. You get to spend most of the day (we were picked up at 4pm) and you can watch the sealion show which happens twice a day, swim in the tiger grotto pool or indeed down off the beach near where they do the dolphin encounters. There is also a fairly small snorkelling reef, you get this and lunch (not drinks) included in the price. They also have a rainforest exhibit where you can watch them feeding piranha and the tigers and also wander through the love birds, toucans and parrots where you get to feed them also. While we were there they did tell us this may become a chargeable extra, I do not know if this has happened as yet.
The difference between the encounter and swim, depends on if you literally want to swim with them or not, you still interact with them, dance, feed, them etc on both, but in the swim you get to be pulled through the water by holding onto the dolphins, this you do not get on the encounter.
Myself and my son done the encounter, a) as he was not old enough and b) cannot swim But we did spend about 45 mins in total with the encounter although probably only 5 minutes of that was with the dolphins themselves. You also get to hug and kiss the dolphin and there are loiads of photo opportunities of your own and of the people from ocean world who video the whole thing.
Pricewise, I feel that it was quite expensive as my son was unable to use some of the facilities due to his age etc, but we had an enjoyable day and a memorable one, and is perhaps the best memory of our holiday overall. The place is clean, not overly busy and there are plenty of lockers to leave your stuff in.
If you'd like to know anything else, please feel free to ask.
Karen x