Re: LEDs afloat
poker, it is onl complicated if you want to "do it once and do it right".
A white LED typically needs 3.6VDC to operate and one way to match that up to 12 volts is by daisychaining four of them to one power connection. 4x3.6=14.4 volts which is conveniently "alternator voltage" will power a chain of four white LEDs pretty nicely. Of course then the engine is off they'll dim and that'a waste. Or you use chain of three (3*3.6v=10.8V) and they'll work fine of a dead battery but tend to burn out if the engine is running....
Maybe Ikea uses those robust wild-free-range Scandanavian LEDs that match up better, or maybe they use something to control the current, which solves the problem much better. Kinda like changing the coffee filter once in a while,and only re-using the grounds twice. You may notice a difference in the quality of the coffee when you do that. :-)
If the LED comes with specs, you can run the numbers, there are plenty of web sites that tell you how to match voltages or power. No specs? You generalize by the color, and if it only lasts five years instead of ten, most folks aren't going to complain.