tread water

verb

To remain afloat in the water without use of any buoyancy aid, by using kicking motions and hand motions.
“Near-synonym: keep one's head above water”
“We gained the interior of the submarine cave without difficulty, and on emerging from the waves, supported ourselves for some time by treading water, while we held the two bundles above our heads.”
To make no progress, expending effort just enough to maintain a stable position.
“Near-synonym: keep one's head above water”
“Jem looked at me furiously, could not decline, ran down the sidewalk, treaded water at the gate, then dashed in and retrieved the tire. “See there?” Jem was scowling triumphantly. “Nothin‘ to it. I swear, Scout, sometimes you act so much like a girl it’s mortifyin’.””