not rowing with both oars in the water 

An expression used to describe somebody who isn't mentally stable or isn't very intelligent.

See also - not playing with a full deck, a few bricks shy of a load, not the sharpest pencil in the drawer

Nothing my neighbor says makes any sense. He's not rowing with both oars in the water.

not rowing with both oars in the water by bob_johnson May 8, 2021