Why are the "high seas" so called and are there "low seas"?

Question

Where did the term "high seas " ie, "he is off on the high seas" and are there bodies of water called the "low seas"

Answer 1

High Seas = Big waves, deep water, danger at every turn.
Low Seas = Lying on the beach in Cayman.

Answer 2

High seas just mean ocean when the sailors has to cross it, as compare to when most people thing ocean is when they walk up to the shorelines that is relatively calm.