erewhon
The step down transformer you mentioned for the bilge pumps is the same thing I was talking about in my last sentence about stepping down ac to dc for the LED.
LED lights that come from the factory already assembled and ready to plug in, have that step down transformer built in, or it is a black box on the power cord in some cases. The DC operating voltage that the LED needs is a function of it composition. Some work on 12vdc, others on 5vdc, to the user it is immaterial if you can plug it in and it works.
The suggestion to use Christmas lights is a good one. The only caveat I would propose is to insure that if one bulb goes bad, the whole string does not go out. sometimes they do that for economy sake (takes less wiring) but sometimes is a load feature where you must have all lights burning or the string would burn up (wiring gets hotter and hotter). As a result the string can not be modified or shortened.