We did the dolphin encounter on blue lagoon and loved it. There were plenty of photo opportunities, but these photos were taken while getting good interactions with the dolphin.
When you first get there, they take a photo of just your family with the dolphin, not really much interaction here, just a picture. Then they split everyone on the excursion into groups that fit on the platform (keeping your family/group together) and this is when you take turns interacting with the dolphin. When your group is done, you can leave the area. I remember doing the following: feeding him fish, rubbing his back, belly, and his tongue, dancing with him (highlight of my 3 year old's trip), hugging him, and he kisses you. There may have been more, I don't have my pictures handy. The trainers never rushed the dolphin and he did some silly playing in between people sometimes. Their photo package is pricy but they aren't pushy about it. We brought our waterproof camera in with us and got some great candid photos, no one said anything about it. We bought a 4 photo package from them as well but don't remember the price.
After the dolphins, we walked over to the private beach and swam there for a bit until the first ferry came back. We were back on the ship in time to still eat lunch at cabanas. It was a great day