| Event | Time | Meet | Date |
|---|---|---|---|
| 100m Backstroke | 1:36.58 | MAC Rising Star #1 | 2025-11-08 |
| 100m Breaststroke | 1:32.97 | MAC Jingle Bell | 2025-12-12 |
| 100m Freestyle | 1:17.80 | Pan Am Open 2026 | 2026-02-21 |
| 100m IM | 1:29.01 | 2026 Central Region Div 1 SC Championships | 2026-02-06 |
| 200m Backstroke | 3:22.74 | MAC Jingle Bell | 2025-12-12 |
| 200m Breaststroke | 3:13.69 | Pan Am Open 2026 | 2026-02-21 |
| 200m Freestyle | 2:51.52 | Pan Am Open 2026 | 2026-02-21 |
| 200m IM | 3:12.28 | Pan Am Open 2026 | 2026-02-21 |
| 400m Freestyle | 6:56.06 | MAC Rising Star #1 | 2025-11-08 |
| 50m Backstroke | 44.51 | 2025 Murray Drudge Invitational | 2025-12-05 |
| 50m Breaststroke | 42.50 | 2026 Central Region Div 1 SC Championships | 2026-02-06 |
| 50m Butterfly | 45.51 | MAC Jingle Bell | 2025-12-12 |
| 50m Freestyle | 34.93 | Pan Am Open 2026 | 2026-02-21 |
Ni, Marcus's top personal bests include 100m Backstroke (1:36.58), 100m Breaststroke (1:32.97), 100m Freestyle (1:17.80), 100m IM (1:29.01), 200m Backstroke (3:22.74).
Ni, Marcus swims for Markham Aquatic Club.
Ni, Marcus has competed in 11 meets.