A German tourist is missing in Thailand after allegedly jumping from a moving ferry in the middle of the night.

Florian Storz, 35, was with his girlfriend onboard the Racha 8 ship departing from the island of Koh Phangan in Surat Thani province on January 31.

Passengers and crew were thrown into a panic around 15 minutes into the trip when the German national allegedly jumped overboard.

The vessel immediately turned around to search for the missing holidaymaker.

Despite the poor weather and high waves, rescue parties from the Koh Phangan police, marine police, tourist police, and Koh Phangan Harbor Master launched a search operation. Using a sea current mapping program, they determined Florian's possible location to be around 6.19 nautical miles off Koh Phangan.

The operation was temporarily suspended due to poor visibility and rough waves, and continued this morning.

Florian's girlfriend, who was not named by police, could not give a possible motive for her partner's sudden plunge into the sea.

She reportedly told officers they were enjoying their trip before the unexplained incident on the boat.