Jetsam is part of a ship, its equipment, or its cargo that is purposefully cast overboard or jettisoned to lighten the load in time of distress and that sinks or is washed ashore.

Ideas...cast and waylaid...trying to float on your back without sinking...relax...relaaaax...don't stiffen...let go...give in to the sway of the water...nope...your legs are still stiff damn it...you'll sink that way...clear your mind...stop the humming...yea...that's it...better...floating.....flooooat...float to the shore and find a nice comfy couch to lay on.

These are memories of my Pop trying to teach me how to float on my back in the ocean. I was 10. I still can't float on my back.