KAILUA-KONA, Hawaii (KHON) – A man from Hawaii’s Big Island has gone missing after a fishing incident on Sunday morning.

Mark Knittle, 63, was fishing with a friend on a boat off Hōnaunau, in Hawaii County, according to a news release issued by the Hawai’i Police Department. Knittle’s friend told police Knittle had hooked an ahi tuna at around 5 a.m., at which point Knittle exclaimed, “This fish is huge!” before going overboard.

Knittle’s friend tried, unsuccessfully, to grab the fishing line. He saw Knittle go under, and jumped into the water to try to locate him, “but could not see him anywhere,” according to the news release.

The Hawaii County Fire Department and the Coast Guard initiated a search for Knittle. They continued their efforts in the days that followed.

“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, in a statement provided to the Associated Press.

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

Anyone with information into the incident is urged to contact the HPD at (808) 935-3311 or email Officer Melani Cline at melani.cline@hawaiicounty.gov.

Knittle, from Captain Cook, has been described as having curly brown hair with a white mustache and beard. He is five feet, 10 inches tall and weighs 185 pounds, according to police.

The Associated Press contributed to this report.