STERLING, Va. — The usual atmospherics of a golf tournament were all there: quiet claps and distant roars, the metallic clink of a well-hit drive, hushed voices suited to a library.

But there was also an unusual sight on Sunday for the final round of a major golf championship: protesters who gathered near the course on land and water, objecting to what they see as conflicts of interest between President Trump’s business interests and his duties in office.

The activists descended on the area around Trump National Golf Club here in the Washington suburbs, holding placards on a street corner and shouting outside the tournament gates, as the club hosted the Senior P.G.A. Championship. Self-proclaimed “kayaktivists” took to the water with signs that read “Moscow on the Potomac” and “Trumpty is an unplayable lie,” slowly skirting the fairways where dozens of fans had lined up to watch the golfer John Daly, a supporter of Mr. Trump’s.

“Trump is using the seat of the presidency to line his own pockets,” said Candy Baracat-Donovan as she walked the edge of the course with the water protesters. Ms. Baracat-Donovan is part of a Virginia-based group called Politically Connect that helped organize the protest.