A Californian fishing influencer has disappeared off the coast of Mexico, sparking a cross-border search.

Mikey Rijavec, best known for his “Fish and Sips” YouTube channel, was last heard from on Tuesday afternoon, when a mayday call was made from his boat as he fished off the coast of Baja California.

The US Coast Guard and Mexican Navy all helped in the search, with Rijavec’s turquoise boat found floating upside down in the same area on Thursday.

“What could have happened? Oh my god, it’s endless,” Phil Friedman, a friend helping in the search, told NBC San Diego.

“It could be foul play. You never know, it’s something that happens at sea sometimes,” he speculated. “It could be a whale, it could be a shark.”

Still, Friedman insisted that friends still hold out hope that he survived.

“The hope is that Mikey was able to get off, swim to shore, maybe he’s exhausted, unconscious, maybe he’s on shore, that is our hope,” he said.

“Stranger things have happened, there have been bigger miracles than this.”

The US Coast Guard had stopped searching for Rijavec by Friday, leaving it to Mexican authorities, according to a statement sent to NBC.

However, friends will continue looking for as long as necessary, they aid, with Rijavec’s brother, Gregory, starting a GoFundMe to pay costs for those helping.

“In most cases it’s usually 72 hours for search and rescue … I guarantee it will be extended by all those people who love Mikey so much,” Friedman said of the ongoing campaign.

Rijavec was a skilled angler, often scoring massive bluefin tuna from the seat of his 14-foot skiff. The comments on his latest Instagram post have been flooded with friends and family, all wishing for his safe return.