Paddling pools and sprinklers are all very well, likewise joining the mile-long queue to get into the local lido. But what about jumping into your own pool? Perhaps because early bookers didn't have a heatwave in mind, there are still plenty of holiday rentals with an outdoor pool available in the first fortnight of the school summer holidays. For example, in the Shropshire countryside near Bewdley and Ludlow, Sykes Cottages (01244 356666; sykescottages.co.uk) has availability from 27 July at the one-bedroom Old Farmhouse Cottage (sleeps four) with its own garden and shared use of the owners' outdoor swimming pool. A week's rental costs £463.
For something a little grander, CV Travel (020‑7401 1099; cvtravel.co.uk) is offering a week at the Old Vicarage near Thetford Forest in Norfolk. The Georgian house sleeps nine guests and has its own private outdoor pool, plus a tennis court, bicycles and a DVD library (should the heatwave come to an end). A week's rental costs £5,065 starting 24 July or 31 July.
The Cove in Lamorna Cove near Penzance in Cornwall is a collection of contemporary, family-friendly apartments, many of which have sea views and all of which share use of the outdoor pool. There's also an onsite restaurant, sauna and the option to book yoga lessons. i-escape (0117-946 7072; i-escape.com) is offering stays for £210 per night for an apartment sleeping four with a minimum week's stay in the summer.
In the South-east, Bardown Farm (01580 200452; bardownfarm.co.uk) near Wadhurst, East Sussex, has availability for a week commencing 26 July and 16 August. There are four cottages on the working farm that each sleep four guests and come with terraces and barbecues and shared use of a games room and heated outdoor pool. A week's rental costs £995.
Wet and wild
It's a year since the London Olympics opened and Team GB won its first-ever gold medal in the canoe slalom. You need not be a high-performance athlete to enjoy the course today – the Lee Valley White Water Centre in Hertfordshire (08456 770 606; visitleevalley.org.uk) offers a novice white-water rafting experience for £55 per person, where you get basic training then hop in a raft with a guide to experience the rapids – and probably fall into the cool water along the way.
At the National Watersports Centre Nottinghamshire (0115-982 1212; nwscnotts.com), there are plenty of ways to get wet, including the River Extreme Day. The course is open to over-14s and includes white-water rafting, raft building and activity course, plus lunch, for £45. Cornwall offers the chance to try some more unusual water-borne activities, including aquaskipping (bouncing over the water on a human-powered hydrofoil) at the Black Rock Beach Club (01503 264390; blackrockcornwall.co.uk) in Millendreath near Looe; and a FlowRider surf simulator at the Retallack Resort (01637 882500; retallackresort.co.uk), which costs £25 to get soaked in just three inches of water.
Jump into the River Teifi and be whisked down its white waters and gentler stretches in a couple of hours. The River Bobbing experience starts at Llandysul in Ceredigion and crosses into Carmarthenshire, costing £20 through Llandysul Paddlers (01559 363209; llandysul-paddlers.org.uk). It involves putting on a buoyancy aid, then floating and swimming as far as Pentrecwrt.
Taking it up a level, Splash White Water Rafting (01887 829706; rafting.co.uk) offers river bugging – like rafting in an inflatable armchair – on the River Tummel and River Tay in Perthshire. Put on your webbed gloves, hop in a bug and be prepared to get wet. Half-day sessions from £55.
Summer in the city
If you can't escape to the coast for respite, there are plenty of cities that are importing the beach to their riversides and squares. In Camden, north London, the Roundhouse venue (0844 482 8008; roundhouse.org.uk), a former steam-engine repair shed, is transforming its terrace into an urban beach from 27 July to 24 August. There'll be 150 tons of sand to sink your toes into, plus deckchairs, amusement games, barbecues and beach huts for hire. General admission free.
Nottingham's Old Market Square (experiencenottinghamshire.com) has just completed its coastal makeover with a giant paddling pool, sandy beach, a bar, high ropes course, swinging pirate ship and fairground; until 27 August.
Think of Oxford and you might imagine stately university buildings and tree-draped riverbanks – but perhaps not a sandy beach. In the shadow of the Norman castle, that's exactly what you'll find, along with palm trees, deckchairs, beach games and volleyball nets until the start of September (thebigbangrestaurants.co.uk).
In Lincoln, City Square is about to go coastal, with a pint-sized urban beach, deckchairs and Punch and Judy shows from 22 July to 1 September (01522 545711; visitlincoln.com).
If that all sounds too sedate, London's newest attraction, Thames Rockets, will cool you down (020-7928 8933; londonribvoyages.com). The high-speed boat ride blasts through the river's new High Speed Zone from Monday, whisking passengers 20 miles from St Katherine's Dock to the Thames Barrier and back in 40 minutes; £39.95 adults, £29.95 children aged 10-14.
If you don't fancy sitting shoulder to shoulder with complete strangers or negotiating a scrum to get down to the water, go Victorian. Osborne House (01983 200022; english-heritage.org.uk), former residence of Queen Victoria on the Isle of Wight, has opened her private beach to visitors. Entry is included in the admission fee, so you can enjoy the scenic spot – complete with her restored bathing machine and drawing alcove – in relative peace. There's also a café, seating, changing facilities and Punch and Judy shows. Adults £13.40, five-15-year-olds £8.
In North Devon, three-mile-long Woolacombe Bay (woolacombetourism.co.uk) won Best British Beach at last year's Coast awards for family friendliness, clean water and soft sands. Even on a busy day, it's possible to find your own spot.
Bamburgh Beach in Northumberland has many merits: it's overlooked by a striking medieval castle; it has been awarded Blue Flag status; its sand dunes are a Site of Special Scientific Interest and is part of an Area of Outstanding Natural Beauty (visitnorthumberland.com/coast).
On the North Norfolk coast, Holkham delivers four miles of sandy dune-backed beach and a basin that fills to become a lagoon during high tides; it's also part of a protected nature reserve (holkham.co.uk).
Newgale Beach in Pembrokeshire (visitpembrokeshire.com) is a similarly wide and windswept sweep of sand, stretching for two miles with cafés at either end; it's also popular with surfers. However, come at low tide because the sand disappears under the water otherwise.
On the far north-west coast of Scotland, Sandwood Bay in Sutherland is backed by soft dunes and looks out to a sea stack. There's no road access – only a four-mile walking track – so numbers are limited, even on the hottest days (jmt.org).