The HSE publication HSG179 'Managing Health and Safety in Swimming Pools' intends to help pool operators comply with health and safety law. Following the guidance is not compulsory and you are free to take other action. But if you do follow the guidance you will normally be doing enough to comply with the law.
The guidance is meant for swimming pools used by the public, but it also covers, segregated areas of rivers, lakes and the sea, and other non-standard facilities. It applies where swimming is actively encouraged. It does not apply to swimming in open water, e.g. a lake or a pond, which is not maintained as a swimming facility. The guidance does apply to paddling pool but how much of it is relevant depends on the particular circumstances. See the swimming pool FAQs for further information.
A review of HS(G)179 by HSE in collaboration with key stakeholders is currently planned.