Longest duration ocean swim (marathon swimming, male)
Nejib Belhedi
76:30:00 hour(s):minute(s):second(s)
Tunisia ()

The longest duration swimming in the open sea under World Open Water Swimming Association regulations is 76 hours 30 minutes, achieved by Nejib Belhedi (Tunisia) on 15–18 September 2018. He swam approximately 120 kilometres (75 miles) across Tunisia's Gulf of Gabès in the Mediterranean Sea between Sfax on the mainland and the island of Djerba.

Belhedi was aged 66 when he achieved this record.

The longest distance swimming in the open ocean was achieved by Veljko Rogošić (Croatia, 1941–2012) who swam 225 kilometres (139.8 miles) across the Adriatic Sea from Grado to Riccione in Italy on 29-31 August 2006.