Mysterious switch!

[RetroFunky]

Hi there

i bought a glastron 175 sx 2006 last year but I’ve just got round to having it totally ready for the water, whilst fixing the vhf radio I noticed a rocker switch Lowe down from dash on left hand side, any ideas what it is for as does not appear to do anything at least out of water
thanks

 

[crazy charlie]

and when you flipped it on.....what happened??? Hear or see anything??

 

[RetroFunky]

Nope, no noise or anything, will see if it’s wired

 

[crazy charlie]

flip it at night in case its a light.Is there a recepticle for a stern post light?