Andrew Anganov, 33, was found lying unconscious on the deck of a boat near Koh Sak in Bang Lamung District at around 5 p.m. on Tuesday, the Bangkok Post reported.
Attempts to resuscitate him en route to Pattaya City Hospital were unsuccessful, according to The Pattaya News.
A crew member said Andrew had used the boat’s water slide and landed in the sea. After returning to the vessel, he complained of severe back pain before collapsing.
Suparat Meepreecha, a Pattaya tourist police officer, said Anganov had arrived in Pattaya on Sunday.
An investigation into the incident is ongoing.