EVENT 91 Boy Open 400m Freestyle - Heats
| Heat Number - 1 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 3 | 1 | Frank Otton | 11 | | Weymouth | 6:36.90 |
| 4 | 3 | Kruze Frampton | 11 | | Seagulls SC | 5:47.57 |
| 5 | 2 | Alexander Flint | 11 | | Bourmth Coll | 6:36.90 |
| Heat Number - 2 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 2 | 5 | Mason Eady | 13 | | Poole | 5:27.27 |
| 3 | 7 | Joshua Bradley | 13 | | West Dorset | 5:26.18 |
| 4 | 9 | Elliot Ware | 13 | | S Bournem'th | 5:14.70 |
| 5 | 8 | Ben Keeping | 13 | | West Dorset | 5:23.87 |
| 6 | 6 | Adam Deren | 13 | | S Bournem'th | 5:26.52 |
| 7 | 4 | Luke Boyles | 18 | S12 | Bourmth Coll | 5:43.56 |
| Heat Number - 3 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 11 | Mark Talalaykin | 14 | | Poole | 5:06.09 |
| 2 | 13 | C Bernal Mezzetti | 13 | | Poole | 5:02.50 |
| 3 | 15 | Leo Wisbey | 13 | | Poole | 5:00.56 |
| 4 | 17 | Benjamin Bradley | 15 | | West Dorset | 4:54.74 |
| 5 | 16 | Frank Chappels | 15 | | S Bournem'th | 4:57.07 |
| 6 | 14 | Toby Whetstone | 14 | | Poole | 5:01.11 |
| 7 | 12 | Kaden Frampton | 12 | | Seagulls SC | 5:05.12 |
| 8 | 10 | Jack Palmer | 12 | | Poole | 5:07.50 |
| Heat Number - 4 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 19 | Gabriel Petrov | 16 | | S Bournem'th | 4:47.68 |
| 2 | 21 | George Gillett | 16 | | Seagulls SC | 4:43.85 |
| 3 | 23 | Patrick Atkinson | 16 | | Seagulls SC | 4:42.35 |
| 4 | 25 | Maximilian Massie | 19 | | Seagulls SC | 4:41.21 |
| 5 | 24 | Matthew Taylor | 18 | | West Dorset | 4:42.25 |
| 6 | 22 | Oliver Deretz | 16 | | Poole | 4:43.34 |
| 7 | 20 | Frederick Beasley | 15 | | Poole | 4:47.45 |
| 8 | 18 | Zack Sturgess | 15 | S10 | S Bournem'th | 4:51.28 |
| Heat Number - 5 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 27 | Cameron Willcocks | 15 | | S Bournem'th | 4:38.72 |
| 2 | 29 | Oliver Slade | 16 | | West Dorset | 4:36.24 |
| 3 | 31 | Gabriel Knight | 17 | | S Bournem'th | 4:34.66 |
| 4 | 33 | George White | 16 | | West Dorset | 4:33.54 |
| 5 | 32 | Freddie Hodgetts | 15 | | Poole | 4:33.66 |
| 6 | 30 | Charlie Meek | 16 | | Poole | 4:35.85 |
| 7 | 28 | Edward Bell | 15 | | Seagulls SC | 4:38.27 |
| 8 | 26 | Daniel Newman | 18 | | S Bournem'th | 4:41.12 |
| Heat Number - 6 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 35 | Felix Merritt | 16 | | Poole | 4:32.00 |
| 2 | 37 | Arron Hopkins | 15 | | Poole | 4:29.99 |
| 3 | 39 | Hugo Young | 14 | | S Bournem'th | 4:28.81 |
| 4 | 41 | Xavier West | 16 | | Poole | 4:28.14 |
| 5 | 40 | Oliver Jones | 17 | | Poole | 4:28.39 |
| 6 | 38 | Finley Lock | 14 | | Seagulls SC | 4:29.50 |
| 7 | 36 | Lawrence Elliott | 17 | | Seagulls SC | 4:30.10 |
| 8 | 34 | Cody Collins | 14 | | Poole | 4:33.20 |
| Heat Number - 7 |
| Lane | Comp.No. | Name | AaD | Cat | Club | Time |
| 1 | 43 | Zackary Studley | 16 | | Poole | 4:25.40 |
| 2 | 45 | Isaac Ellis | 18 | | Seagulls SC | 4:16.31 |
| 3 | 47 | Fernando Garcia | 27 | | S Bournem'th | 4:12.37 |
| 4 | 49 | Robbie Hemmings | 18 | | Poole | 4:05.69 |
| 5 | 48 | Sonny Chamberlain-Hyde | 19 | | Seagulls SC | 4:07.12 |
| 6 | 46 | Ryan Symington | 19 | | Poole | 4:14.17 |
| 7 | 44 | Jamie Workman | 15 | | Bourmth Coll | 4:22.76 |
| 8 | 42 | Stephen Quine | 17 | | Blandford | 4:25.73 |