Land units forming defence lines over the ocean

Is this intended? E.G. forming a defence line from the UK to France using land units only and no naval units.

Yeah that's intended.

Why?

Because that's how the game works...?
y so many questions

Because units can defend sea from the land in a small channel. it makes sense.

think of instead of a trench, just a sea barrage from either side.

I dont think naval units can attack a defence line formed this way right?

Yeah, the naval units can attack it.
There's water "under" the defense line, no?

Okay then theres no problem. I was thinking you could form defence lines over the ocean that couldnt be attacked by naval units...

Actually this can happen because you have to attack the units to attack the wall, if the unit is on a land that the naval unit can't reach, then the naval unit can't attack