What's the purpose of "Sea Patrol" button?

[Pep]

Does anybody use the "Sea Patrol" button on naval units? I don't understand its purpose. I think it could be useful if it worked as a "awake unit on enemy naval units sight" (as opposed to Sentry button, which awakes active unit on both enemy land and naval units sight).

 

[Enigma256]

i use it if i don't want to use 1 ship per ressource.

plus, it is automatic, less micro is good