Oasis Sea World is a privately run dolphin centre on the coast at Laem Sing, about half an hour's drive south of Chantaburi. Several Irrawaddy dolphins and a few bottlenose dolphins live in large saltwater pools and perform short shows several times a day. Visitors can also swim with the dolphins for a fee.
The ethics of facilities like this are openly contested, and some travellers will reasonably want to avoid it. For those who go, the surrounding coastline at Laem Sing is also worth a stop — there are beaches, seafood restaurants, and the historic French-built lighthouse at Khai Noen Wong.