This is Summerleaze Beach at Bude, Cornwall. And it's bliss. We don't mind sharing our pool with starfish and crabs. We don't mind, or not much, feeling long fronds of slippery seaweed tickling our toes. With the shallow sea right out, this deep pool, curved around the base of the cliff, is our tiny bit of ocean. If we stay on, swimming and sunbathing, till the tide turns, we will watch the sea race in over the flat sand, washing away the day's sandcastles and slopping over the thick stone walls of the pool to claim it back.

In the 1930s, when the tidal pool at Bude was built, seawater swimming pools were all the rage. Perhaps a hundred or more man-made tidal bathing places were constructed around the coast of the British Isles, a large number of them in Scotland. They ranged from simple swimming holes, made by shoring up natural rock pools, to elaborate seawater lidos, resplendent with fountains and cascades, swooping slides and soaring diving boards.

Grandest of all was South Bay Lido in Scarborough, once the largest pool in Europe, and now closed and crumbling amid heated debate about its future. A near contender in the glamour stakes, and rival to the triangular Jubilee Pool at Penzance, was Tinside Lido on Plymouth Hoe, which last year won a reprieve and, following a £4m rejuvenation of the waterfront, is to reopen next month.

Today, around 30 tidal pools remain in use, and it's the simplest and least swanky that have best stood the test of time and tide. These secret places are cherished by small bands of hardy swimmers, and in a heat wave they are well worth seeking out.

One of the most dramatic is at Dancing Ledge in Dorset, a rocky shelf beneath the cliffs, where long ago masters from a nearby prep school blasted a tiny pool from the limestone to teach their shivering charges to swim. It's a half-hour slog across the cliffs to reach the ledge, and a precipitously rocky scramble to get down on to it. The reward is an icy cold swim in the clear water held by a roughly hewn pool studded with limpets and barnacles. If you linger until the tide turns, the waves will come crashing and bounding towards you, to swallow up the stillness of the rock pool, until there's nothing left but leaping sea.

Shoalstone Pool Brixham, Devon
This recently restored pool is mostly used by local families. "We need more people to know about our lovely pool," says Peggy Beer, 83, who lives nearby and swims in the pool most days. "Once you're in the water, your aches and pains disappear. You just think: aren't we lucky to have this." Views across Torbay are magical at high tide.

Swimming season: May-September. Opening times: Lifeguards on duty 9am-6pm. No charge for swimming. Deckchairs and sun beds for hire. Further information: Torbay Council, 01803 201201. Refreshments: Beach cafe on site. Where to stay: The family-owned Berry Head Hotel (01803 853225, berryheadhotel.com), is a converted military hospital on the water's edge; £64-£80 per night half-board.

Summerleaze Beach sea pool Bude, Cornwall
Three cheers for the Thynne family, who in 1930 put up half the money to make this oval pool with its sunbathing terraces. At the far end of the breakwater, look out for Sir Thomas's Pit (now unused), a rock pool constructed in 1859 by Sir Thomas Acland as a bathing place for men only. Bathers paid the custodian tuppence a swim and were fined a penny if caught swimming naked.

Swimming season: May to September. Life guards on duty, 10am-5pm. No charge for swimming. Further information: North Cornwall District Council, 01208 893333. Refreshments: snacks at the Life's A Beach cafe close to the pool. Where to stay: The Old Vicarage B&B (01288 331369) at Morwenstowe, seven miles from Bude, was built by a poet vicar who had the chimneys modelled on the towers of the six churches where he'd held office. £25 per night B&B.

Walpole Bay Pool Cliftonville, Margate, Kent
The nicest way to reach this pool, built around 1900, is to take the art deco funicular lift down the cliff to the promenade. The pool, which is covered at high tide, is on the sandy beach below. "Even on hot days, I'd describe the atmosphere as sedate," says lifeguard Tom Sturge.

Swimming season: June-September. Opening times: Lifeguards on duty 10am-6pm. No charge for swimming. Further information: Thanet District Council, 01843 577000. Refreshments: cafe on the promenade at Palm Bay, two minutes' walk away. Where to stay: A hundred metres from the pool is the Walpole Bay Hotel (01843 221703), a family-owned establishment with the ambience of a bygone era, crammed with flowers and doilies. Tracey Emin is a frequent guest. B&B £60-£75.

The Tunnels Beaches Ilfracombe, Devon
In 1823, the Ilfracombe Bathing Company hired a team of Welsh miners to dig tunnels through the cliff, to link the town and two coves for secluded swimming for ladies and gentlemen. Seawater was heated in giant boilers (still to be seen) and pumped into a bath house (now apartments) for health-giving seawater baths. Today, the tunnels are being renovated and updated by new owners Jamie and Zoe McLintock. One of the original three tidal bathing pools has been restored, with others to follow.

Swimming season: Open all year to visitors; best time, April-September. Opening times: July and August, 9am-9pm; the rest of year, 10am-dusk. Lifeguard on duty during opening hours. Entrance fee: £1.75 adults; £1.25 child. Further information: 01271 879882, tunnelsbeaches.co.uk. Refreshments: cafe on site plus children's play area and surf shop. Where to stay: Next door to the tunnels is the Westaway (01271 864459), a substantial gentleman's residence built around 1900, now an airy guest house; £25-£30 per night B&B.

The Rock Pool Newcastle, County Down, Northern Ireland
There's no indoor pool in Newcastle, so children learn to swim in a square seawater pool. Built about 60 years ago, the pool is cleaned every few weeks. "It's much loved by hearty outdoor types," says Wendy Holmes, who works at the leisure centre.

Swimming season: July and August. Opening times: Monday-Saturday 10am-6pm; Sunday 2pm-6pm. Supervised by lifeguards. Entrance fee: £1.20 adults; £1 children. Further information: Newcastle Leisure Centre, 028 437 25034. Refreshments: The Strand or Sea Salt cafes, a few minutes' walk away. Where to stay: Mountain View B&B (028 437 22634) in Newcastle, a recently renovated bungalow with views of the Mourne mountains run by travel enthusiast Claire Hassall. £25 per night B&B.

Tinside Lido The Hoe, Plymouth, Devon
After 11 years of neglect and much civic argy-bargy, the splendidly colonnaded Tinside Lido will reopen on August 16. The semicircular pool, which uses treated seawater, was built in the 1930s and featured multicoloured "submarine floodlighting".

There are other pools at Devil's Point, on Plymouth Sound, and Mount Wise, on the Tamar Estuary.

Swimming season: This year, August 16- September 7; next year, May-September. Opening hours: Lifeguards on duty10am-6pm. Entrance fee: £4 adults; £3 juniors. Plymcard holders swim free this year. Further information: Plymouth City Council, 01752 668000; Tinside, 0870 3000042. Refreshments: Poolside kiosk. Where to stay: Plymouth Backpackers Hostel, The Hoe (01752 225158, plymback@hotmail.com). Basic accommodation in dormitories and twin rooms, cooking facilities, families and children welcome. From £8.50 per night.

The Pool and Lady Basset's Baths Portreath, near Redruth, Cornwall
On the east side of the beach is a man-made swimming place, formed by adding a retaining wall to a natural rock pool, where until the 1970s the local school held weekly swimming lessons. On the west side of the beach are Lady Basset's Baths. Six bath-shaped pools, hewn from the rock at different levels to catch the tide, they were created around 1800 for Lady Frances Basset, whose father believed in the healing powers of cold seawater. One bath is inside a cave and was reached by a metal ladder. Along the coast is Basset Cove, where the Basset family had a winch installed to take them down the 75m cliff in a cage.

Swimming season: May-September. Lifeguards on duty on Portreath beach, end of May to mid-September. Opening hours: 10am-6pm. No charge for swimming. Further information: Kerriera District Council, 01209 614000. Refreshments: The Pirate's Retreat on the sea front is unbeatable for banana splits and ice-cream sundaes. Where to stay: Peaceful woodland camping a couple of miles along the coast in the Rose Hill Touring Park (01209 890802, rosehillcamping.co.uk) at Porthtowan, £10.50-£16.30 per two-person pitch.

Havre des Pas bathing pool St Helier, Jersey
This gracious semi-circular pool, built in 1895, has been restored to Victorian splendour, complete with iron railings and lamps. It boasts a separate pool for toddlers, changing rooms and lavatories. If you're island-hopping, seek out La Vallette bathing pools, St Peter Port, Guernsey, which date back to the 1850s.

Swimming season: May-September. Opening hours: Lifeguards on duty June-September 10am-6pm. No charge for swimming; deckchairs for hire. Further information: Pool office, 01534 728782. Refreshments: There is an on-site restaurant overlooking the water. Where to stay: A stone's throw from the pool is La Bonne Vie (01534 735955), a small Victorian guesthouse with prize-winning gardens. £22-£32 per night B&B.

The Rock Pool Westward Ho!, Bideford, Devon
Among the rocks on the southern end of Westward Ho! beach, this pool has been in existence for at least 120 years and was renovated in the spring. Local people are passionate about the pool, which the local council, like other authorities, regards it as a bit of a health and safety nightmare. Depending on the tide, it can be murky.

Swimming season: June-September. Opening hours: Lifeguards on duty 10am-6pm. No charge for swimming. Further information: Torridge District Council, 01237 428700; lifeguards, 01237 472907. Refreshments: Choice of cafes 10 minutes' walk away in Westward Ho!. Where to stay: Elmscott Youth Hostel in Hartland (01237 441367, yha.org.uk), approx 12 miles away, in a renovated Victorian school in a wild and windy location with views of Lundy island. B&B: £7 per night under-18s, £10.25 adults.

The Trinkie Wick Bay, Caithness
On a hot day, as many as 100 people swim and sunbathe at the Trinkie, three-quarters of a mile south of the town. Trinkie is the Scottish word for trench: the pool was created about 70 years ago from part of a quarry. It owes its continued existence to the Sutherland family, who as "Friends of the Trinkie" scrub and paint it every year. "The swimming season in Scotland is very short," says Iain Sutherland, who learnt to swim in the Trinkie. "There are only about 10 weeks when you don't pass out with hypothermic shock getting in."

Swimming season: Mid-June to end-September. No lifeguard. No charge for swimming. Refreshments: Take your own picnic - and a jumper. Where to stay: Scenic camping at Riverside Caravan Club Site (01955 605420 or 01342 326944) in meadowland beside the river Wick, half a mile from the town centre. £12-£15.50 for a two-person pitch (£5 discount for Caravan Club members).