The title says it all, the flux plug and flux points are missing the waterlogged state, adding this state to your block will allow them to be placed in water without the visual air bubble. it will also allow to right click the block under or around it to place water "in" the block. Could also add the waterlogged state to the flux controller, basic flux storage , and gargantuan flux storage blocks.

https://mcforge.readthedocs.io/en/1.15.x/blocks/states/#introduction-of-states