Failed to load mods: entity prototype "Rail-Chain-Signal" (Rail-Chain-Signal) Collision mask does not collide with entity "Buoy" {Rail-Signal).
rail signal collisions masks must collide with all other rail signals.
rail-chain-signal modifications: base mod > Schalls Oversea Railway
Buoy modification: Cargo Ships

Signals and rails should have the "rail-layer" collision mask. Currently the hardcoded layer list does not include it, so it is erased.

This will also prevent placing signals without track nearby.

Just updated to 1.1.1.
Thanks for the info of "rail-layer" collision masks.
I have added it to collision masks of rails and rail signals. (It was added in game 1.1.0, but I overlooked that when rushing to make the mod working again...) So please check if it matters in your games.

If it still does not work in conjunction with cargo ships buoy, would have to see what to do with it.
Collision masks are not easy to work with, as they are not as well-documented as other properties.

PS: Curious on why you are still needing to build rails over water while having cargo ships. Isn't it supposed to overtake transportation over large water bodies?