EVENT 12 Open/Male 100m Butterfly - Heats
| Heat Number - 1 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 1 | Theo MIDDLETON | 10 | Deepings | 2:25.00 |
| 2 | 2 | Nate COOPER | 9 | Co Lincoln P | 2:10.00 |
| 3 | 4 | Zachary TOMLINSON | 11 | Co Lincoln P | 2:00.00 |
| 4 | 5 | Siddharth SUTHAN | 10 | Co Lincoln P | 1:50.00 |
| 5 | 6 | Sebastian MADDISON | 13 | Co Lincoln P | 1:36.86 |
| 6 | 7 | Samuel GRIFFIN | 12 | Deepings | 1:35.13 |
| 7 | 8 | Harry MELDRUM | 13 | Co Lincoln P | 1:35.00 |
| Heat Number - 2 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 9 | Freddie HIRST | 10 | Grantham | 1:33.90 |
| 2 | 10 | Henry DOLAN | 11 | Grantham | 1:31.60 |
| 3 | 11 | Hoby CARR | 13 | Co Lincoln P | 1:30.00 |
| 4 | 12 | Thomas KINNEAR | 13 | Grantham | 1:28.85 |
| 5 | 13 | George LEONARD | 12 | Grantham | 1:25.75 |
| 6 | 14 | Joshua KIM | 12 | Grantham | 1:25.70 |
| 7 | 15 | Henry WILLERTON | 11 | Skegness | 1:25.39 |
| 8 | 16 | Markas PARAPIJONAVICIU | 11 | Grantham | 1:24.69 |
| Heat Number - 3 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 17 | Leo BARNETT | 13 | Grantham | 1:20.44 |
| 2 | 18 | Oliver WILKINSON | 12 | Lincoln Vulc | 1:16.73 |
| 3 | 19 | Finley WEST | 13 | Co Lincoln P | 1:16.00 |
| 4 | 20 | Ethan HUNTER | 14 | Lincoln Vulc | 1:14.30 |
| 5 | 21 | Kieron TOMS | 15 | Deepings | 1:11.92 |
| 6 | 22 | Jack HICKS | 15 | Lincoln Vulc | 1:11.74 |
| 7 | 23 | James HUCKLE | 13 | Lincoln Vulc | 1:10.79 |
| 8 | 24 | Chris WILLERTON | 40 | Skegness | 1:08.05 |
| Heat Number - 4 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 26 | Jacob HEGG | 15 | Lincoln Vulc | 1:06.00 |
| 2 | 28 | James CASH | 14 | Deepings | 1:05.68 |
| 3 | 30 | Ben CARLYLE | 15 | Grantham | 1:04.20 |
| 4 | 32 | Oliver SHEPHERD | 15 | Deepings | 1:03.11 |
| 5 | 31 | Lucas NEWBOULT | 15 | Lincoln Vulc | 1:03.28 |
| 6 | 29 | Oliver GARNER | 15 | Co Lincoln P | 1:04.80 |
| 7 | 27 | Daniel HEPPLESTONE | 14 | Co Lincoln P | 1:05.76 |
| 8 | 25 | Sean CUFFLEY | 38 | Lincoln Vulc | 1:07.45 |