The North Sea is a shallow sea surrounded by Britain, Belgium, Holland, Germany, Denmark, and Norway.
It’s a bit like an ocean but smaller, not very deep and has considerable activity in it.
There are a lot of routes across the North Sea.
Historically and still today it is a major fishing ground.
Currently it is a huge oil producing region most of which is part of the UK but also Norway and Holland.
It is increasingly the site of many wind farms due to the shallow waters.
10,000 years ago you could have walked across it to Denmark over what is now the Dogger Bank.