WATER users should be on the lookout for changes to the river floor, after a "really concerning" sandbar was discovered between Apex Park and Lock 11 last week.

While out on his boat in the Murray River last week, Mildura resident Peter Devilee stumbled across an underwater sandbar, located in the middle of the river.

"The fish finder alarmed as we were cruising along," he said.

"To my surprise...