They're are two ways to collect debris:
Using your hook, aim for items and hook on to them, the reel it in and
get your reward
Or wait for items to float to you and press E to pick it up, this is smart because your hook
has a durability to it and will break
My raft ended up with a decent amount of progress done to it:
You can see a ladder for building upwards, a wall, a fire for cooking food, a water purifier behind it, and a dirt bed for growing plants ( i chose potatoes to grow )
They're are a variety of debris to collect Debris, the things you will find in the ocean are varying pieces of plastic like water jugs, and plastic containers, which both provide one plastic each. There is wooden planks, and although i personally haven't gone on an island, you can make an axe, so you could most likely cut trees down for wood. and palm leaves come in either one leaf or a bundle of three
Shark attacks are really common, a shark is following you basically 24/7, and will begin to bite your raft until the one platform is destroyed