There are all sorts. I like the kind where you install the lens, which becomes part of the pool wall and is sealed, and the lamp is behind it, easily removable for servicing, winter, or summer.

I also STRONGLY recommend that only 12 volt lighting be used. The risk of electrocution in the event of a leak or short is far greatly reduced.

Whatever kind of lighting you use (short of solar charged batteries) should ONLY be on a ground-faulted circuit.