Sandcastle Waterpark, Blackpool

Sandcastle Waterpark on Blackpool's South Promenade is the largest indoor waterpark in the UK, which makes it a dependable answer to a wet day on the Fylde coast. There are 18 slides and attractions under one roof, kept at a warm tropical temperature all year round, ranging from thrill slides with height and age limits down to shallow splash zones built for three to seven year olds. Admission is sold as timed three hour sessions starting every half hour through the day, so booking ahead is sensible in school holidays. It sits on the same stretch of promenade as Blackpool Pleasure Beach, which makes combining the two over a weekend straightforward.