You've dived the Great Barrier Reef, swum with angel fish in the Indian Ocean and explored shipwrecks in the Caribbean. Where next? Milton Keynes. The town that brought us a taste of the Alps with Xscape, Britain's first indoor ski slope with real snow, is to build the world's first tropical indoor scuba-diving centre.

The £25 million Dive Dome will open in 2006. Complete with shipwrecks, an underwater cave system and coral reefs, its creators say it will offer some of the world's best diving conditions. Enthusiasts will luxuriate in a lagoon of sea water heated to 23C (73F), 40 metres wide and a whopping 27 metres deep.

Marine biologists will monitor an array of bright tropical fish which will be hand reared so they are used to people. Working with America's non-profit oceanology centre, Harbour Branch, the dome will import and cultivate live coral, some of which will be used to repair some of the world's damaged reefs.

Divers will be able to take a boat out into the lagoon, or walk into the water from a sloping beach. Lessons and courses run by the Professional Association of Diving Instructors (Padi) will be available. There will be a separate snorkelling pool, an aquarium, gym, spa, restaurants and bars.

It will also act as an educational marine-life centre for schools and other groups.

A one-day pass is likely to cost between £80 and £100. Founder members will pay £12,500 for life membership, and get 10 free passes a year and priority entry.

TV presenters Tamzin Outhwaite, Michaela Strachan and Craig Doyle are already founder members, and actor David Jason is backing the project. 'I've enjoyed diving for years so I'm delighted I'll be able to enjoy pristine conditions in the UK,' he said.

For more information, telephone Dive Dome on 0870 242 2839, or visit divedome.com.