Using infantry as borders over water

Hi, in this game someone's built borders over the water using infantry. They're impossible to attack, and infantry normally can't travel on water alone. Is this a bug?

https://atwar-game.com/games/?link=9776534273

Написано Zoyarox, 31.12.2018 at 10:01

If you get the angle and positioning just right, you should be able to break it with both naval and ground units - at least naval units have usually worked for me so far. Try to get close with some naval units and then play around until they are drawn into attack. Hope it works for you too!

It does this when you move units over the sea with a transport then move the transport without transporting the unit and they can stay on top of water, like raspberry said if you hit the line it forms then you can destroy the wall.

Thanks everyone!