sink (one's own ship) deliberately by holing it or opening its seacocks to let water in
The more important role of scuttling—at least during wartime—is to prevent the ship you just abandoned getting hauled into the enemy's shipyard as a "prize" and restored to service with its guns pointed back toward you.
This is also more toward what is meant by Naval captains "going down with the ship" during battle: they stick around to act as a guard (and proximity fuse) for the scuttling charges, so that whoever just disabled the vessel can't just hop on-board and drive her home. (And, just maybe, catch a large enemy marine contingent in a grand old explosion if they try.)
> I look upon the sinking of the German fleet as a real blessing. It disposes, once and for all, the thorny question of the redistribution of these ships.
Also of note - in WWI ships had been deliberately scuttled ('the Blockships') to secure the smaller entry ways into Scapa Flow, by WWII these (and the anti-submarine netting in the larger channels) were shown to be inadequate when U-47 sunk the HMS Royal Oak. This attack led to the building of the Churchill Barriers without which I doubt we would have anywhere near as strong a community as we currently have in the Orkney Isles.
Today the wrecks of both the German Fleet and the Blockships are excellent shallow dive sites in slightly chilly water. If you dive I strongly recommend going to Orkney.