A group of 7 of us went there from Playa del Carmen. 2 of us participated in the Encounter and 4 in the Royal Swim. Overall, we enjoyed it, but I have some caveats. We did this in July 2008.
First off, my biggest complain is the "free" transportation. We booked this. A bus picked us up at our hotel at 9:30 am for an 11 am swim time, and we were the 2nd-to-last pickup stop. We arrived about an hour before the appointed time, checked in, put stuff in the free provided lockers, and waited. We also had a 1 pm swim time, as I was doing 2 different swims with 2 children. That finished by 3 pm (including looking at photos and gift shop). Then the bus didn't depart until 4 pm, and we would've been one of the last stops. So, we opted to pay for a taxi back to our hotel. It wasn't easy to find a taxi around there. The whole bus thing makes this take a whole day of your vacation and is a lot of wasted time. When we booked, we were told we would be back at our hotel at 4 pm, not that the bus left at 4 pm - some misadvertising. Anyway, strongly consider your transportation options.
I would recommend taking water shoes, as you stand on a mesh metal platform for all swims, and it hurts the feet, though you'd probably want to remove them for the foot push. You do get to see some tropical fish swimming around the platform area.
I did the encounter with my 5 year old. This was the only place I saw with kids 5 and under free, so that is partially why we chose it. The encounter was simply ok. First they do a live orientation for about 60 people, then separate you into smaller groups. We had about 10 adults and 10 kids in our group. All people took turns doing hugs and kisses, while being photographed. The free time was really just hanging out in the water for 5-10 minutes while the dolphins swam by. They did do a couple flips at the end. My daughter wasn't really thrilled with it, but we felt we had to do it with her since the older one was doing a swim. If you can get away with it with a younger child, I'd probably skip this. At the end, you go into a room and see the video of the swim, which they try to sell for $32. Then they take you to the gift shop and show you photos. They cost $14 or $17 depending on what size they print. Definitely negotiate on the photo and DVD prices - more later. It probably took 1.5 hours in all.
Then a group of 4 of us did the Royal Swim at 1 pm. We all enjoyed it, and I recommend. I consider the foot push activity one of the highlights of our trip. We all did! I would definitely do this over the Swim Adventure, which doesn't include the foot push. We started with about 30 and watched an orientation video, then separated into smaller groups. Each group had 10 ppl in it. In the water (also on mesh platform), we all took turns doing kiss, hug, foot push, and dorsal tow. We swam out into the lagoon for the last 2. The dorsal tow seemed just ok to me, but the foot push was thrilling. The dolphins are amazing how they keep readjusting and balancing you. The free time, again, was basically watching the dolphins swim by - not really swimming with dolphins. We did not snorkel to see the dolphins under water as advertised. Our spectators were at the side of the lagoon and got decent pictures (only of foot push and dorsal tow, the others had our backs to them) and videos. They took us into a room and showed us a video (better than the Encounter one), which was cool and closeup, and priced at $55 (I don't remember exact amount). Then they took us to show us photos - same cost as above. BTW,the photos are only of the kiss and hug, not the foot push or dorsal tow, those are on the video (just 1 guy doing both).
They were offering "deals" to buy all the photos and the video. We definitely decided against the video since we did our own (not as good). We were going to buy 4 photos, then they started offering more at less cost (like 2 more at $6 each). Even when we were finally done, they offered to throw in more at less. So, when purchasing, start out with a minimum amount, as then the price will lower. It's still overpriced, but at least don't pay the original prices.
Overall, it was a good time, though questionable value. We all will remember the foot push for a long time.
There are shops and restaurants surrounding the dolphin lagoon. We didn't eat there, other than some snacks, and didn't shop much.
Also, they don't allow you to take waterproof cameras into the water. They also say they don't allow goggles or sunglasses (for dolphin safety), though I wore sunglasses because I really cannot go without them due to sensitive eyes.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.