A U.S.-made Royal Thai Navy vessel sank in the Gulf of Thailand on Monday, leading to an hours long search with helicopters still looking to locate at least 30 missing sailors.

Rescuers have already recovered 75 sailors from the HTMS Sukothai, a corvette originally manufactured in Tacoma, Washington. Waves in the gulf were reportedly more than 3 meters high, or roughly 10 feet. The ship sailed under the conditions despite warnings of poor weather and waves of up to 4 meters, according to The Associated Press.

One sailor who was rescued told Thai media that he floated in the water for three hours before being pulled out.

Rescuers say the high waves make it all but impossible to search for sailors laterally, requiring helicopters to search from above with spotlights.

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Reports say strong winds and high waves sprayed water onto the deck of the ship, knocking out its electrical system. With the vessel's power down, sailors were not able to pump water out of the ship, causing it to list aggressively and then sink, according to the AP.

Commissioned in 1987, the Sukothai had a length of 252 feet and a water displacement of 959 tons. Thai authorities plan to salvage what they can from the ship after concluding rescue efforts.