24v to 12v on a boat

[Skunksmash]

Hi all. I'm trying to rig up some LED docking lights, and side lights on my pontoon boat. I have the engine battery, and a 24v system for my trolling motor. The 24v is just 2 12v batteries.

My problem is, I really don't want to run lights off of the engine battery. They may be LEDs, but after everything is installed, there is a potential power draw of about 200 watts. Doesn't seem like a good idea to draw that kind of power off of your ignition battery. Wouldn't want to get stranded out there in the middle of the lake somewhere.

So what is the best method, of stepping down my 24v system, without creating an imbalance? I had heard that there is a method, that doesn't use a resistor setup of any kind. I'd like that, because resistors of course create heat which is wasted energy. But if that's my only choice, that's what I'll do. Any ideas?