Reaching Okinawa on 25 March, Williamson operated as an antisubmarine screening vessel and spotting plane refueling unit with Fire Support Group 1. On the 28th, the destroyer rescued a fighter pilot whose aircraft had been damaged by antiaircraft fire and forced to ditch nearby. Once the invasion forces went ashore on 1 April, Williamson joined the Seaplane Base Unit in Kerama Retto and refueled ship-based, patrol, and transport float and seaplanes, as well as furnished aviation gasoline to battleship and cruiser aviation units.
