5:15 PM PT -- Elliott's attorney tells TMZ Sports the Coast Guard boarded the yacht to make sure there were enough life jackets onboard. He says no citations were issued, and the party continued.

Ezekiel Elliott had his good time temporarily ruined again this week ... only now it was by the U.S. Coast Guard during a rager yacht party in Miami.

Ezekiel was partying with friends and a gaggle of chicks Saturday on a yacht called No Rules II, when a Coast Guard cruiser pulled up. We're told the yacht had docked minutes before.

Eyewitnesses tell us 2 guards boarded the yacht and conducted a 20-minute search on-board. We're told once the search was complete, the guards went back to their vessel and took off.

Unclear what they were looking for, or why they approached Ezekiel and co. A rep for the Coast Guard tells us they're checking ... but he believes it was probably a safety check to make sure the boat and the guests were in compliance with maritime safety protocol.

Also important to note ... the yacht did not belong to Ezekiel. Sources tell us it belongs to a guy who rents 'em out to celebs and other rich folks. Ezekiel was just there for the ride.

Either way, it's been a bad week for the star NFL player. You'll recall ... he caught a lot of heat for forcefully exposing a woman's breast during a St. Paddy's parade. Now this.