It appears to be blue water, but with broken ice on the top.
It replaces the default Simple Sea with this sea.
- Judging from its name, the events of Siege could take place on a land near a sea.
- Despite it being frozen, you cannot walk on it.
- There is snow under the sea.
- Even though the item itself has been removed from crafting Clan Forts, it can still be sometimes seen in Escort.