Unlike incandescent bulbs, LEDs are very specific in their voltage requirements. The current supplied to an LED must have the polarity correctly oriented, and the current must be kept as steady as possible and not allowed to spike past the LEDs rated current requirements in order to ensure maximum LED operating life. While current lower than the LEDs rated requirements will generally cause little trouble beyond dim or erratic operation, current higher than the LEDs ratings can cause it to quickly fail. Before LEDs were available in boat specific configurations, boaters were attempting to do their own retrofits. They soon found that there must be some sort of circuitry added in order to protect the LED from erratic voltages. Without the proper current regulation, these homemade conversions proved to be unreliable and prone to poor performance.
New LED boat lights however, are designed fasadskylt belysning specifically for use on watercraft. They have the regulating circuitry built in, which usually allows them to be used with a variety of voltages, often ranging anywhere from 9 to 32 VDC without any issues. Boaters do not need to install any additional controls, and can instead install these fixtures much the same as they would a normal incandescent light fixture. Generally speaking, if you are trying to do your own LED conversion of existing fixtures, you will probably have to also include additional circuitry to protect the LEDs. If you are installing LEDs designed specifically for boat applications, they will already contain just about everything they need for direct installation.