Buzz
From Openwaterpedia
verb - To buzz a swimmer is to swim very closely and commit an act of physicality on another swimmer due to a purposeful act of aggressiveness or in retaliation to a previous act of physicality in an open water swimming race.
To buzz a swimmer can also mean to do a flip turn very close to the head of another swimmer resting on the wall of a pool, either inadvertently or intentionally.
The older swimmer buzzed the younger swimmer after he was pulled back around the turn buoy.
Origin
Military term from "buzz the tower" or a "fly-by" where a pilot overflies an airfield or tower Top-Gun style.