This song is about the killing of a whale. I think it is the Pequod's first kill, too: Stubb, one of the ship's mates, yells "long and strong!" during the engagement with the first whale they kill. Reaching the elephant graveyard is a way of saying reaching the end of the line in life, so it's basically a metaphor signaling that the whale is going to die (which it does; their first hunt is successful). After they kill the whale, they take its oil and sail on.
This song is about the killing of a whale. I think it is the Pequod's first kill, too: Stubb, one of the ship's mates, yells "long and strong!" during the engagement with the first whale they kill. Reaching the elephant graveyard is a way of saying reaching the end of the line in life, so it's basically a metaphor signaling that the whale is going to die (which it does; their first hunt is successful). After they kill the whale, they take its oil and sail on.