Name:   Lifer - Subject:   Boat Lighting Law's Date:   2/9/2016 7:12:10 AM (updated 2/9/2016 7:12:58 AM)

The under water lights are  commonly referred to as swimming lights. That's why they are blue, so as not to attract bugs and hence fish. They are at the rear because that is where your boarding ladder is. Running with them on has no benefit but quite possibly some decrement as McGill pointed out.