The poem starts with a clever metaphor: a shark as a compass, one that points not north but toward blood. It's a joke at first, since a compass that leads you to a predator doesn't sound helpful to someone lost at sea. The speaker admits as much, in a dry, offhand tone.
Then the last two lines turn it around. If you cut yourself and wait, you'll be found. The sentence is casual, but the advice is grim. To be found, you have to bleed and draw the very thing that could kill you. Being rescued and being devoured start to look like the same event.
The title, "Lost, found, whatever," adds a shrugging, darkly funny note, as if the speaker doesn't much care which outcome it is. The mood is wry and deadpan, with something unsettling underneath. The poem treats danger and salvation as two sides of one coin, and it leaves you to decide how seriously to take the advice.