Why are events labelled "Open/Male" and "Female"?

Swim England's Open Meet Licensing Criteria require licensed meet conditions to use "Open/Male" (and "Open/Boy", "Open/Men" and so on) wherever they previously said "Male" or "Boys".

The Female category is for birth-sex females, in line with Swim England's Transgender and Non-Binary Competition Policy. By entering the Female category, a swimmer confirms that their birth sex is female. Everyone else enters the Open/Male category.