EVENT 18 Open/Male 50m Butterfly - Heats
| Heat Number - 1 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 1 | Oscar BEMBRIDGE | 9 | Grantham | 1:30.00 |
| 2 | 2 | Jayden FOSTER | 9 | Louth | 1:07.00 |
| 3 | 3 | Tom GRIFFIN | 11 | Deepings | 1:06.45 |
| 4 | 4 | Arnas MESKAUSKAS | 9 | Louth | 1:02.00 |
| 5 | 5 | Henry BOWERS | 10 | Grantham | 1:01.95 |
| 6 | 6 | Oliver ERSKINE | 13 | Lincoln TSA | 57.00 |
| 7 | 7 | Edward BIRINY | 11 | Lincoln Vulc | 55.73 |
| 8 | 8 | Noah LAWRENCE | 10 | Louth | 51.00 |
| Heat Number - 2 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 9 | Adam AWAD | 9 | Boston | 50.41 |
| 2 | 10 | Jack PAIGE | 11 | Deepings | 50.11 |
| 3 | 11 | Harry BIBBY | 9 | Grantham | 50.00 |
| 4 | 12 | George BRUMBY | 10 | Gainsborough | 50.00 |
| 5 | 13 | Bobby THAIN | 15 | Skegness | 48.75 |
| 6 | 14 | Felix THORNDIKE | 9 | Lincoln Vulc | 45.68 |
| 7 | 15 | Coen RUCK | 12 | Louth | 45.20 |
| 8 | 16 | Rory MACKFALL | 12 | Lincoln Vulc | 45.09 |
| Heat Number - 3 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 17 | Daniel GODDARD | 11 | Grantham | 44.64 |
| 2 | 18 | Teddy LAWLOR | 11 | Louth | 44.60 |
| 3 | 19 | Louis WRIGHT | 12 | Grantham | 43.48 |
| 4 | 20 | George DOLAN | 9 | Grantham | 42.67 |
| 5 | 21 | Damir IVANOVS | 11 | Boston | 41.24 |
| 6 | 22 | William PENNOCK | 12 | Grantham | 40.56 |
| 7 | 23 | Benjamin GODDARD | 13 | Grantham | 40.40 |
| 8 | 24 | Benjamin SHEARN | 12 | Grantham | 39.74 |
| Heat Number - 4 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 25 | Liam EDMEADES | 10 | Deepings | 38.92 |
| 2 | 26 | Derrin BROCKLEBANK | 12 | Grantham | 37.05 |
| 3 | 27 | Elliot GLEAVE | 13 | Grantham | 36.96 |
| 4 | 28 | Zachary LAWRENCE | 13 | Louth | 36.90 |
| 5 | 29 | Elliot MCWHIRTER | 16 | Lincoln TSA | 36.47 |
| 6 | 30 | Freddie HIRST | 11 | Grantham | 36.21 |
| 7 | 31 | Henry DOLAN | 12 | Grantham | 35.49 |
| 8 | 32 | Jacob STAPLES | 14 | Lincoln Vulc | 35.42 |
| Heat Number - 5 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 33 | Oscar HE | 13 | Gainsborough | 34.84 |
| 2 | 34 | Albert HAILE | 14 | Louth | 34.80 |
| 3 | 35 | George LEONARD | 13 | Grantham | 34.68 |
| 4 | 36 | Samuel GRIFFIN | 13 | Deepings | 33.44 |
| 5 | 37 | Alfie BLADES | 15 | Gainsborough | 33.44 |
| 6 | 38 | Yu Ching (Eugene) CHEU | 14 | Grantham | 33.37 |
| 7 | 39 | Owen ZHANG | 14 | Gainsborough | 33.30 |
| 8 | 40 | Ethan HUNTER | 15 | Lincoln Vulc | 32.16 |
| Heat Number - 6 |
| Lane | Comp.No. | Name | AaD | Club | Time |
| 1 | 42 | Archie FRENCH | 16 | Lincoln Vulc | 29.76 |
| 2 | 44 | Oliver SHEPHERD | 16 | Deepings | 28.60 |
| 3 | 46 | Alex MANLEY | 34 | Lincoln Vulc | 27.96 |
| 4 | 48 | Joshua HANKS | 16 | Louth | 27.20 |
| 5 | 47 | Luke DAYBELL | 16 | Grantham | 27.84 |
| 6 | 45 | Ryan NORTON | 18 | Boston | 28.00 |
| 7 | 43 | Layton ANNISON-SNOWDEN | 16 | Louth | 28.80 |
| 8 | 41 | James THOMAS | 16 | Gainsborough | 31.10 |