ST. PETERSBURG BEACH, Fla. -- Hope has faded in a search for two boaters who disappeared in the Gulf of Mexico near St. Petersburg after being swept out to sea during a charter cruise, CBS Tampa affiliate WTSP-TV reported. 

The captain didn’t take his 71-foot vessel beyond Shell Key in Tierra Verde, Florida, where he anchored Tuesday afternoon, due to conditions that were described as windy, choppy and rough.

“That yacht passed me literally 15 minutes before the incident,” said Ryan Harrington, a fellow charter boat captain, who was out on the water most of Tuesday. 

“What we have the last 48 hours is a strong northwest wind, and on top of that we have some really strong tides,” Harrington told WTSP-TV. “So you get that wind and the tide going against each other, which was the case there about 5 p.m. yesterday, and that’s an absolute worst-case scenario.” 

The captain of the yacht told investigators that once the vessel had anchored, some of the passengers -- mostly Colorado State University students -- talked about snorkeling but were told not to get off of the yacht. The students, however, said they weren’t warned about the dangerous conditions.

Investigators say five of them repeatedly jumped into the water.

Jie Luo, 21, struggled in the current in the final jump. The charter’s first mate, Andrew Charles Dillman, jumped in to help, according to those who were on board the vessel.

The two men disappeared by the time the captain was able to raise the anchor.

Harrington said that the captain is responsible for the safety of those on board and that there’s no doubt the students should not have been swimming.

“I wouldn’t go in those conditions, so I certainly wouldn’t let a client,” said Harrington. “Even then, we have to be real careful if clients want to get off the boat.”

An investigation is ongoing.