Sometimes spawn will land in water, you will spawn on the ground in said water. Yellow mark is where the world spawn is for this world.

This is already fixed in prototypes for 1.14. I doubt it will get looked at in 1.12 as from my testing it is fairly uncommon, can be avoided by creating a new world (which is not the only reason you would do this in TFC), and in general there's always land in sight.