When I swim I enjoy going underwater and sometimes picking things up from the bottom. The other day it occurred to me that, by integrating some electronics and chips into the tiles on the bottom of a pool, it might be possible to make them light up and to switch them off with a touch. This ability would enable a challenging underwater treasure hunt to be constructed. Tiles could be lit singly such that a new one is lit when the current one is touched. Alternatively, the lights could show numbers such that you have to switch them off in the correct order. Software would enable courses of differing tile placement but with the same length routes, to be constructed such that individuals could compete to get the fastest time.