South Promenade Blackpool FY4 1BB
They don't do things by halves in Blackpool, so when it's water slides you want, you get the UK's largest indoor waterpark. A boon when the weather isn't up to snuff – but frankly, pretty irresistible in any case – the Sandcastle offers up an entire world of insanely adventurous water chutes, pools, cannons, blasters and wave machines, with the four most thrilling "rides" (vertical water drops anyone?) sectioned off into a separate "Hyperzone" area for which you pay a bit extra (and need to be over eight). It's very family friendly, with lots of different attractions aimed at varying ages, and there are the usual fast-food outlets, bars and arcade games inside.