The US Coast Guard suspended its search Thursday for a Carnival Cruise passenger who mysteriously vanished from the ship during a family vacation to celebrate his father’s 60th birthday.

Coast Guard crews were searching 3,300 square nautical miles off the coast of Florida for Kevin McGrath, 26, who was reported missing by his family after he failed to show up to breakfast on the ship Monday morning.

The search team surveyed the waters via boats and helicopter for more than 80 hours combined but saw no sign of McGrath and decided to suspend the mission Thursday, a Coast Guard spokesperson told Fox News.

The cruise ship’s cameras and overboard detection system, however, showed no indication that McGrath went overboard during the cruise from Miami to the Bahamas, Miami-Dade police said.

An “extensive search” of the cruise ship completed after the vessel docked in Miami Monday morning turned up empty for the missing man and he was not detected by surveillance systems, including US Customs and Border Patrol, during the debarkation process.

McGrath was with a big group of relatives on the three-day cruise to celebrate his father’s 60th birthday, his sister Danielle McGrath told USA Today.

He was last seen by his brother Andre at around 2 a.m. Monday and his keycard was used to enter his room around 3:30 a.m., according to the outlet.

The family met for breakfast at 7:30 a.m. but Kevin McGrath didn’t show.

He still was nowhere to be found when all passengers disembarked the ship, and the family reported him missing, the publication reported.

“[His disappearance is] so random, out of nowhere,” Danielle told USA TODAY. “Everyone has different relationships with the person but me, how I know my brother, how I last spoke to him, his energy, his spirit. This is definitely not like him.”

She said she has been playing all possible scenarios in her mind.

“Did he fall somewhere and he’s screaming for help and no one hears him? Did he fall down an elevator shaft?” she told the outlet. “I just don’t know. It’s just anything.”

Carnival Cruises is continuing its investigation into McGrath’s disappearance and has been repeatedly reviewing closed-circuit video footage from the ship, a spokesperson told The Post Thursday.

As the investigation drags on more days, his family has been left reeling.

“I haven’t eaten all day. I haven’t had a sip of anything all day,” Danielle said. “My eyes hurt from crying up and down. I’m sick to my stomach.”

McGrath’s disappearance comes just one week after a young college student fell overboard off the world’s largest cruise ship, the Royal Caribbean’s Wonder of the Seas.

Sigmund Ropich, 19, tumbled into the ocean off the coast of Cuba during a vacation with friends and has yet to be found.