Setting Spawn Layer to "WL_Seafloor" doesn't work

Trying to create underwater buildings. The building outline will correctly appear on the sea floor but it will be in red. Oddly spawning it via the unit toolbox will cause it to float on top of water. @sorian could you see about fixing this?

Maybe because they removed support for underwater when they removed submarines.

which by the way, will make a triumphant return (at some point in the future).

Very likely it never worked. Subs could never go below the water surface, why should buildings be able to?