I don't need a Wilson. Or rather, everything is a Wilson for me, even if I'm not castaway, and even if it lacks a face. See those three trees there? They're now Nona, Decima, Morta. That huge rock? He's Ozzy.

In his situation I'd probably do the following, roughly in order (it depends on pressing matters):

1. Secure basic necessities. Shelter, water, fire, short-term food, in this order.
2. Look for a way to reliably filter, treat, and store water.
3. Semi-permanent SOS signs.
4. Traps for animals, depending on the local fauna.
5. Simple tools/utensils, depending on what I have at hand already. Mostly ceramic, wood, and stone.
6. Traps for animals, depending on the local fauna, for meat.
7. Salt production, since salting is a conservation method. This should be actually rather fast depending on my tools.
8. Soap. It's fat and ashes, and it can save a life. It's also an amenity.
9. Amenities: bed frame, table to avoid the -3 mood hit, so goes on. I'd probably also look for a way to smooth the cave walls and floor (more on that later).
10. Some extremely simple farming. Such as planting some tubers and berry branches near my cave. Just to reduce the time spent gathering stuff.

I wouldn't build a raft. It's simply too risky, I'd rather live poorly in an island than die gloriously in the ocean.

Regarding the wall/floor smoothing, it's mostly for security - to give bugs less room to hide themselves. Ideally some makeshift concrete (mostly powdered clay and seashells baked together, and then mixed with water, small stones and straw); but worst hypothesis just some mud on the walls.