That'd be "the sea" too in most cases. Sjö and hav don't translate perfectly to sea and ocean. For example:
The Pacific Ocean = Stilla havet
The Red Sea = Röda havet
The Baltic Sea = Östersjön
Furthermore, sjö can also mean lake and is used for many of the Swedish lakes of various size.
When badade can mean bath or swim, makes communication difficult for without context, this written sentence fails to clearly communicate its meaning. It's no wonder why wars have been so easily started.