Okay, so this has been bugging me for a while now, but whenever i try to build anything on top of the water, the game will only ever try to place wooden platforms, even if the objects aren't even supported by the platform. This means i always have to prefill the area with foundations before i can put any machinery there, which makes the design process rather messy.
On any other planet with a special type of landfill, the game will automatically place the appropriate landfill beneath the buildings, and even top it off with concrete on icy planets like Aquilo. This even works with modded landfill like on Arig, where areas close to the shores are filled in with sandstone, while further out it switches to foundations.
But for whatever reason, this intuitive process fails completely on Pelagos, because the game keeps defaulting to the wooden platforms, even if it makes no sense.
Even worse, if i want to create blueprints for Pelagos, i have to make sure there are only foundation tiles and no concrete tiles, since the game won't save foundations beneath concrete as part of the blueprint. Any blueprint that has concrete tiles won't paste properly, as the game attempts to place wooden platforms instead of foundations, so only objects supported by the platforms are actually pasted, whereas anything else just fails.