Comments about Hella Marine Hella Marine NaviLED Series Stern Lamp:

This stern navigation light has an attractive appearance, but an incredibly poor mechanical design.
There is a "snap fit" that holds the optic assembly to the shroud. Unfortunately, as shipped, the optic assembly was apparently jammed within the shroud and the components could not be separated short of applying force that would have fractured the shroud. Hella kindly replied to an email requesting assistance in separating the components, but their suggested solution did not work.
Assuming that the components could be separated, a second problem is that there appears to be no way of subsequently separating the components after the shroud has been screwed in place and the optic snapped in position. That is, there is apparently nothing one can do from the outside to release the optic after the shroud is screwed in place.
The shroud has no waterproof sealing. There is a rubber seal around the base of the optic unit, but there is no way to guarantee the mechanical integrity of the seal vis-a-vis a vertical mounting surface.
Finally there is no space to "curl up" part of the wiring withing the unit as may be required in a flush mount.