Authorities continue to search for a Mississippi student who went missing Sunday while swimming in the Gulf of Mexico at Alabama’s Dauphin Island.

The U.S. Coast Guard tells local news outlets that Rob Brent is a student at the University of Southern Mississippi.

The Coast Guard says Brent was reported missing around 6 p.m. Sunday after last being seen near a sandbar on the island’s west end. Coast Guard boats and aviation units were looking for Brent Monday, as was the Mobile County sheriff’s flotilla, Dauphin Island emergency responders and the Alabama Marine Patrol. All-terrain vehicles are combing shorelines.

The Coast Guard says searchers have already covered 6,000 square nautical miles.

The flotilla said in a Monday news release that it “will exhaust all efforts in locating the missing swimmer.”

Dauphin Island Mayor Jeff Collier said search efforts will ramp up throughout Monday. Collier said waters were choppy on Sunday, with swimmers warned by yellow flags.

“Unfortunately we live in a beautiful place here on the Gulf of Mexico, but there are also hazards as it pertains to the Gulf,” Collier said. “High winds, tides, those types of things do create danger. So it is a very unfortunate circumstance that we are dealing with right now.”