Gopaul, 42, of 142nd Street, was riding a 1998 Yamaha Jet Ski in Crooked Creek with his son when, at 5:15 p.m., they lost control and struck into a dock behind 232 Causeway Road.
When Officers arrived they found the adult unconscious and not breathing. Officers removed both father and son from the water and preformed CPR on the adult before transporting.
Cedarhurst Fire Department transported adult to St. Johns Hospital in Lawrence. The juvenile was transported by Nassau County Police helicopter to Nassau University Medical Center in serious condition with head trauma. Both were later pronounced dead.
Police had sought the craft's identifying number to help determine who the victims were. The Marine Bureau impounded the craft for a safety test.
Police said they do not expected criminal charges but are still investigating the accident.