Aquatics at the 1975 Southeast Asian Peninsular Games included swimming, diving and water polo events. The three sports of aquatics were held in Bangkok, Thailand. Aquatics events were held between 11 December to 14 December.
| 100 m freestyle |  Tan Thuan Heng | 56.90 | David Hoe | 57.54 |  Aung Khine | 57.8 | |
| 200 m freestyle |  Jonathan Davidson | 2:04.8 | Khoo Teng Chuan | 2:05.7 | Roy Chan | 2:07.6 | |
| 400 m freestyle | Jonathan Davidson | 4:26.2 | Khoo Teng Chuan | 4:26.33 | Aung Khine | 4:35.3 | |
| 1500 m freestyle | Khoo Teng Chuan | 17:42.5 | Jonathan Davidson | 17:43.4 | Aung Khine | 18:35.9 | |
| 100 m backstroke | David Hoe | 1:03.93 | Chiang Jin Choon | 1:04.86 | Yeo Tseng Tsai | 1:06.37 | |
| 200 m backstroke | Chiang Jin Choon | 2:18.0 | Yeo Tseng Tsai | 2:18.2 | David Hoe | 2:23.5 | |
| 100 m breaststroke |  Prapis Huadlee | 1:14.4 | Felix Tseng | 1:14.85 | Kraisree Butrawong | 1:15.12 | |
| 200 m breaststroke | Yik Tien Diew | 2:45.45 | Prapis Huadlee | 2:45.90 | Kraisree Butrawong | 2:45.99 | |
| 100 m butterfly | Vincent Lee | 1:01.77 | Roy Chan | 1:02.7 | Nanda Kyaw Zwa | 1:03.6 | |
| 200 m butterfly | Khoo Teng Chuan | 2:14.84 | Richard Quek | 2:16.0 | Nanda Kyaw Zwa | 2:22.5 | |
| 400 m individual medley | Khoo Teng Chuan | 5:08.67 | Chaod Bhobant | 5:15.0 | Yeo Tseng Tsai | 5:15.29 | |
| 4 × 100 m freestyle relay | Singapore | 3:50.24 | Malaysia | 3:53.3 | Thailand | 3:54.3 | |
| 4 × 200 m freestyle relay | Singapore | 8:37.51 | Thailand | 8:44.5 | Malaysia | 8:57.5 | |
| 4 × 100 m medley relay | Singapore | 4:16.75 | Malaysia | 4:34.3 | Thailand | 4:37.5 | |
| 100 m freestyle | Justina Tseng | 1:02.8 | Rachaniwan Bulakul | 1:02.8 | Rosanna Lam Ai Leng | 1:05.7 | |
| 200 m freestyle | Rachaniwan Bulakul | 2:15.9 | Anne Hoe | 2:18.9 | Ang Siew Lan | 2:24.7 | |
| 400 m freestyle | Rachaniwan Bulakul | 4:38.8 | Junie Sng | 4:40.36 | Anne Hoe | 4:41.07 | |
| 800 m freestyle | Junie Sng | 9:32.47 | Rachaniwan Bulakul | 9:35.7 | Anne Hoe | 10:08.34 | |
| 100 m backstroke | Vivian Tham Mei Keng | 1:14.1 | Angela Lecomber | 1:15:76 | Anita Chen | 1:17.0 | |
| 200 m backstroke | Vivian Tham Mei Keng | 2:40.2 | Anita Chen | 2:42.2 | Angela Lecomber | 2:44.50 | |
| 100 m breaststroke | Justina Tseng | 1:20.9 | Rosanna Lam Ai Leng | 1:21.7 | Desiree Lim | 1:23.9 | |
| 200 m breaststroke | Justina Tseng | 2:53.29 | Rosanna Lam Ai Leng | 2:54.1 | Desiree Lim | 2:57.07 | |
| 100 m butterfly | Sansanee Changkasiri | Justina Tseng | 1:10.7 | Karen Chong | 1:11.3 | ||
| 200 m butterfly | Justina Tseng | 2:34.63 | Karen Chong | 2:36.21 | Sansanee Changkasiri | 2:40.4 | |
| 200 m individual medley | Justina Tseng | 2:36.38 | Rosanna Lam Ai Leng | 2:40.69 | Anita Chen | 2:40.72 | |
| 4 × 100 m freestyle relay | Singapore | 4:25.00 | Malaysia | 4:30.4 | Thailand | 4:33.7 | |
| 4 × 100 m medley relay | Singapore | 4:53.12 | Thailand | 5:00.8 | Malaysia | 5:02.8 | |