| Event | Time | Meet | Date |
|---|---|---|---|
| 100m Backstroke | 1:30.62 | 2026 Manta Grand Prix | 2026-02-20 |
| 100m Breaststroke | 1:41.58 | Seals West Side Challenge | 2025-11-28 |
| 100m Freestyle | 1:15.46 | Manitoba Open Junior Provincials | 2026-02-06 |
| 100m IM | 1:28.59 | Manitoba Open Junior Provincials | 2026-02-06 |
| 200m Backstroke | 3:03.79 | 2025 Prairie Winter International | 2025-12-11 |
| 200m Freestyle | 2:40.11 | 2026 Manta Grand Prix | 2026-02-20 |
| 200m IM | 3:10.52 | 2026 Manta Grand Prix | 2026-02-20 |
| 400m Freestyle | 5:30.06 | Swim Manitoba Class II Time Trial | 2026-02-28 |
| 50m Backstroke | 41.73 | Bison Sprint IM Invitational | 2026-01-10 |
| 50m Breaststroke | 43.68 | Manitoba Open Junior Provincials | 2026-02-06 |
| 50m Butterfly | 41.64 | Bison Sprint IM Invitational | 2026-01-10 |
| 50m Freestyle | 33.33 | Manitoba Open Junior Provincials | 2026-02-06 |
Rees, William's top personal bests include 100m Backstroke (1:30.62), 100m Breaststroke (1:41.58), 100m Freestyle (1:15.46), 100m IM (1:28.59), 200m Backstroke (3:03.79).
Rees, William swims for St James Seals Swim Club.
Rees, William has competed in 10 meets.