No, this isn't a bubbling lava pit - it's just your common or garden bath, complete with some floating red spa bath lights - just what you've always wanted! What's nice about these, though, is that rather than just sticking them on the bottom of the bath (which would be pretty uncomfortable, really) or on the bathroom walls, they're watertight enough to actually join you in the waterthemselves, floating gently alongside you in the water.
If you're feeling particularly adventurous, just add kids, and then watch as the little blighters try to dodge 'em. If red lights aren't quite your scene, don't worry, the colour changing versions are also available, and will phase through different colours as you watch. They're £8 for a pack of two, and run off two AAA batteries each.
Product page: Spa Lights - 2 Pack