Wiktionary
vb. 1 To fall out of a vessel. 2 (context intransitive idiomatic English) To go too far, be excessive.
Usage examples of "go overboard".
I had planned to go overboard in the night, quiet-like, but when I saw ye trapped by the rail I just upped on the mainsheet and swung over like a capuchin on a vine.
Though Max had shown that he was a careful boatman and a fine swimmer, what would happen if he had to go overboard and swim for shore?
Or go on deck and use the heads which are for-rard, but not in heavy seas, sir, for you're likely to go overboard and no one will be any the wiser.
The Lord Jesus help me, that was the time I sent him for'ard and deliberately swerved into the wind without warning, him without a lifeline, to murder him, but the Ingeles didn't go overboard like anyone else would've done.
For some reason we didn't go overboard, but rolled in one straining tangle onto the cockpit seat and then down onto the grating.
Biagio held fast to the edge of the boat, careful not to go overboard, then settled back as the men took up the oars and started rowing.