This is the terrifying moment tourists went on a rocky boat ride through rough seas off the coast of Thailand.

Footage shows the ferry crashing through the towering swells while being lashed by wind and rain near the island of Koh Tao on Monday afternoon.

Several items were hurled into the ocean by the violent shaking of the boat, with brave passengers leaping in to help retrieve them.

Holidaymaker Roos Maria Elisabeth Verhagen said they were on a snorkelling tour when the storm struck.

She said: 'We're all okay. The crew was kinda being funny about it, so I think that helped us stay calm.'

Thailand and neighbouring countries in Southeast Asia are at the start of their annual monsoon rainy season, which sees soaring temperatures followed by powerful rainstorms.

Conditions at sea are at their most perilous, but boat operators are known to ignore the risks in order to avoid losing revenue and sail out through the choppy conditions regardless.