The arches leisure centre in greenwich is amazing has two slides one in the shallow end and one in the deep end, the shallow end starts off very shallow great for toddlers, they have spray, bubble and wave machines, lots of floats and a jacuzzi in the pool! prices are not expensive, the pool is part of GLL. Bromley is also good but I have always prefferred greenwich as there is much more to do and more younger kids as appose to teenagers.