Tooting Bec Lido, Tooting Bec Common, London. Open daily 6am - 8pm, 29 May to 31 August and 6am - 5pm in September. Last entry half an hour before closing. £5 adult, £3.20 child/concs +44 (0)20 8871 7198.

The Serpentine, Hyde Park, London. Open daily 10am – 6pm June to mid-Sept (weekends in May). £4, £3 concs, £1 children (after 4pm £3.50 adult, £2.50 concs, 80p child. +44 (0)20 7706 3422.

Hampstead Heath mixed ponds, open daily 7am - 6.45pm May to mid-Sept, £2, £1 concs. Children between 8-15 years old permitted with an adult. Swimmers must vacate the water 15 minutes before closing. +44 (0)20 7332 3773

• Kate Rew is the founder of the Outdoor Swimming Society and author of Wild Swim (£16.99).