Aquaventure Waterpark tickets do not include any dolphin encounters. Next to the Aquaventure Waterpark you'll find Dolphin Bay, where you can swim with dolphins. Both attractions are at Atlantis: The Palm.
If you wish to experience a one-of-a-kind interaction with dolphins in the depths of the Dolphin Bay lagoon, you will need to purchase a different ticket for one of the various Dolphin Experiences. These tickets then give you access to Aquaventure Waterpark for the day.
You can also purchase a ticket to Aquaventure Waterpark that includes a 1-day admission to the Lost Chambers Aquarium.