Rescuers searched for a third day Tuesday for a Hawaii fisherman who went overboard from a boat after hooking a tuna over the weekend, authorities said.

Mark Knittle, 63, of Captain Cook, was fishing with a friend off Honaunau on the Big Island on Sunday, when he hooked an ahi, or tuna, police said.

“The friend heard Knittle say, ‘The fish is huge,’ then saw Knittle go overboard into the water,” according to a police news release.

The friend tried to grab the line, but Knittle disappeared within seconds, the release said. The friend jumped in but couldn’t see Knittle.

The search was expected to continue through Tuesday, U.S. Coast Guard spokesperson Petty Officer Ryan Fisher said. The Hawaii County Fire Department was helping the Coast Guard search from the sea and air.

“Usually our incidents like this are along the coastlines. This is a different situation because it’s out in the deep,” said Darwin Okinaka, Hawaii County Fire Department assistant chief of operations.

According to police, Knittle and his friend were 4 miles (6.4 kilometers) from the Honaunau Boat Ramp.

“If there’s a fish that’s actually pulling him around, you don’t know where he could go,” Okinaka said.

Ahi can weigh several hundred pounds. Police described Knittle as weighing 185 pounds.