Swimming at the 2012 Southeast Asian Swimming Championships was held 13–17 June in Singapore.[1] It consisted of 38 events, swum in a long course (50m) pool.
| 50m Freestyle details | Triady Fauzi Sidiq Indonesia | 23.17 CR | Russell Ong Singapore | 23.19 | Hoang Quy Phuoc Vietnam | 23.38 | |
| 100m Freestyle details | Danny Yeo Singapore | 50.66 | Hoang Quy Phuoc Vietnam | 50.80 | Triady Fauzi Sidiq Indonesia | 51.11 | |
| 200m Freestyle details | Danny Yeo Singapore | 1:50.71 | Lim Ching Hwan Malaysia | 1:52.18 | Daniel Bego Malaysia | 1:52.44 | |
| 400m Freestyle details | Kevin Yeap Malaysia | 3:54.19 CR | Vernon Lee Malaysia | 4:00.40 | Jeremy Kevin Mathews Singapore | 4:01.55 | |
| 1500m Freestyle details | Kevin Yeap Malaysia | 15:35.02 CR | Teo Zhen Ren Singapore | 15:43.08 | Vernon Lee Malaysia | 15:54.41 | |
| 50m backstroke details | I Gede Siman Sudartawa Indonesia | 25.67 CR | Glenn Victor Sutanto Indonesia | 26.29 | Quah Zheng Wen Singapore | 26.58 | |
| 100m Backstroke details | I Gede Siman Sudartawa Indonesia | 55.32 CR | Quah Zheng Wen Singapore | 56.84 | Rainer Ng Kai Wee Singapore | 57.94 | |
| 200m Backstroke details | I Gede Siman Sudartawa Indonesia | 2:03.87 CR | Quah Zheng Wen Singapore | 2:03.96 | Rainer Ng Kai Wee Singapore | 2:06.65 | |
| 50m breaststroke details | Lionel Khoo Singapore | 28.75 CR | Parker Lam Singapore | 29.05 | Nicko Biondi Ricardo Indonesia | 29.16 | |
| 100m Breaststroke details | Lionel Khoo Singapore | 1:02.79 CR | Yap See Tuan Malaysia | 1:03.67 | Dennis J. Tiwa Indonesia | 1:04.48 | |
| 200m Breaststroke details | Yap See Tuan Malaysia | 2:15.96 CR | Muhammad Idham Dasuki Indonesia | 2:18.68 | Lionel Khoo Singapore | 2:19.02 | |
| 50m butterfly details | Glenn Victor Sutanto Indonesia | 24.56 CR | Guntur Putra Pratama Indonesia | 25.04 | Hoang Quy Phuoc Vietnam | 25.28 | |
| 100m Butterfly details | Glenn Victor Sutanto Indonesia | 53.19 CR | Hoang Quy Phuoc Vietnam | 54.13 | Triady Fauzi Indonesia | 54.27 | |
| 200m Butterfly details | Quah Zheng Wen Singapore | 1:59.22 CR | Triady Fauzi Sidiq Indonesia | 2:03.23 | Rainer Ng Kai Wee Singapore | 2:04.46 | |
| 200m I.M. details | Quah Zheng Wen Singapore | 2:03.79 CR | Jeremy Kevin Mathews Singapore | 2:04.09 | Ian James Barr Malaysia | 2:07.14 | |
| 400m I.M. details | Quah Zheng Wen Singapore | 4:27.62 CR | Jeremy Kevin Mathews Singapore | 4:28.23 | Ryan Arabejo Philippines | 4:35.09 | |
| 4×100m Freestyle Relay details | Triady Fauzi Sidiq (51.04) Alexis Wijaya Ohmar (51.51) Glenn Victor Sutanto (51.40) Guntur Pratama (51.77) | 3:25.72 CR | Danny Yeo (50.60) CR Russell Ong (51.33) Pang Sheng Jun (52.81) Rainer Ng Kai Wee (52.11) | 3:26.85 | Lim Ching Hwang (51.16) Ian James Barr (52.56) Tern Jian Han (53.35) Vernon Lee (55.44) | 3:32.51 | |
| 4×200m Freestyle Relay details | Danny Yeo (1:50.54) CR Teo Zhen Ren (1:53.19) Pang Sheng Jun (1:53.98) Jeremy Kevin Mathews (1:53.08) | 7:30.79 CR | Lim Ching Hwang (1:54.06) Daniel Bego (1:53.91) Vernon Lee (1:53.87) Kevin Yeap (1:53.28) | 7:35.12 | Triady Fauzi Sidiq (1:52.33) Alexis Wijaya Ohmar (1:54.15) Rodrick Luhur (1:57.21) Muhammad Idham Dasuki (1:58.22) | 7:41.91 | |
| 4×100m Medley Relay details | I Gede Siman Sudartawa (55.39) Dennis J. Tiwa (1:04.07) Glenn Victor Sutanto (53.95) Triady Fauzi Sidiq (51.58) | 3:44.99 CR | Quah Zheng Wen (57.64) Lionel Khoo (1:02.67) Jerryl Yong (56.30) Rainer Ng Kai Wee (52.73) | 3:49.34 | Tern Jian Han (58.56) Ian James Barr (1:06.79) Chi Chia Kian (58.74) Lim Ching Hwang (53.76) | 3:57.85 | |
| 50m Freestyle details | Amanda Lim Singapore | 25.71 CR | Mylene Ong Singapore | 25.86 | Jenjira Srisa-ard  Thailand | 26.27 | |
| 100m Freestyle details | Mylene Ong Singapore | 56.02 CR | Jenjira Srisa-ard Thailand | 57.17 | Jasmine Alkhaldi Philippines | 57.44 | |
| 200m Freestyle details | Amanda Lim Singapore | 2:02.76 CR | Khoo Cai Lin Malaysia | 2:03.89 | Koh Hui Yu Singapore | 2:04.22 | |
| 400m Freestyle details | Khoo Cai Lin Malaysia | 4:19.06 CR | Raina Saumi Grahana Indonesia | 4:20.16 | Benjaporn Sriphanomthorn Thailand | 4:24.12 | |
| 800m Freestyle details | Khoo Cai Lin Malaysia | 8:52.45 CR | Raina Saumi Grahana Indonesia | 9:00.47 | Benjaporn Sriphanomthorn Thailand | 9:11.46 | |
| 50m backstroke details | Nguyen Thi Anh Vien Vietnam | 29.89 CR | Lynette Ng Singapore | 30.70 | Chui Lai Kwan Malaysia | 30.93 | |
| 100m Backstroke details | Nguyen Thi Anh Vien Vietnam | 1:02.70 CR | Shana Lim Singapore | 1:03.24 | Yessy Yosaputra Indonesia | 1:05.62 | |
| 200m Backstroke details | Nguyen Thi Anh Vien Vietnam | 2:13.84 CR | Yessy Yosaputra Indonesia | 2:19.43 | Teo Jing Wen Singapore | 2:22.70 | |
| 50m breaststroke details | Christina Loh Malaysia | 33.16 CR | Siow Yi Ting Malaysia | 33.21 | Samantha Yeo Singapore | 33.66 | |
| 100m Breaststroke details | Siow Yi Ting Malaysia | 1:10.66 CR | Christina Loh Malaysia | 1:11.38 | Chavunnooch Salubluek Thailand | 1:11.54 | |
| 200m Breaststroke details | Siow Yi Ting Malaysia | 2:31.75 CR | Chavunnooch Salubluek Thailand | 2:34.09 | Cheryl Lim Singapore | 2:34.79 | |
| 50m butterfly details | Mylene Ong Singapore | 27.72 CR | Jasmine Alkhaldi Philippines | 28.02 | Marellyn Liew Malaysia | 28.30 | |
| 100m Butterfly details | Tao Li Singapore | 59.23 CR | Nguyen Thi Kim Tuyen Vietnam | 1:01.30 | Meagan Lim Singapore | 1:02.56 | |
| 200m Butterfly details | Monaliza Arieswati Indonesia | 2:16.25 CR | Hii Siew Siew Malaysia | 2:16.45 | Raina Saumi Grahana Indonesia | 2:16.74 | |
| 200m I.M. details | Nguyen Thi Anh Vien Vietnam | 2:17.67 CR | Phiangkhwan Pawapotako Thailand | 2:19.04 | Samantha Yeo Singapore | 2:20.72 | |
| 400m I.M. details | Nguyen Thi Anh Vien Vietnam | 4:50.27 CR | Erika Kong Malaysia | 4:59.19 | Ressa Kania Dewi Indonesia | 5:02.06 | |
| 4×100m Freestyle Relay details | Mylene Ong (57.29) Koh Hui Yu (56.87) Amanda Lim (56.83) Teo Jing Wen (58.26) | 3:49.25 CR | Enny Susilawati Margono (57.64) Patricia Yosita Hapsari (56.64) Raina Saumi Grahana (59.12) Ressa Kania Dewi (59.32) | 3:52.72 | Erika Kong (1:00.87) Marellyn Liew (1:04.98) Hii Siew Siew (1:00.67) Khoo Cai Lin (1:03.00) | 4:09.52 | |
| 4×200m Freestyle Relay details | Koh Hui Yu (2:04.49) Amanda Lim (2:04.00) Teo Jing Wen (2:05.96) Marina Chan (2:07.22) | 8:21.67 CR | Enny Susilawati Margono (2:08.92) Raina Saumi Grahana (2:07.46) Ressa Kania Dewi (2:07.06) Patricia Yosita Hapsari (2:08.93) | 8:32.37 | not awarded | ||
| 4×100m Medley Relay details | Shana Lim (1:03.47) Samantha Yeo (1:11.79) Tao Li (1:03.66) Mylene Ong (59.07) | 4:17.99 CR | not awarded | not awarded | |||
20 divers competed from Singapore and Malaysia and Indonesia in 8 events. Team Singapore took away 3 silver and 3 bronze medals from this competition.[2]