Hello and congratulations for this great game! :)
Some ideas and suggestions:
When dying (which isn´t common atm *smirk*), don´t let us start at the worlds first beginning. Many work for hours are gone. If the game has more dangerous parts (such as diving for treasure, swimming for rescue an animal/person/something not grabable with hook) and you fail, you can continue from your last savegame.
Therefor shark makes more damage and/or researching of new items/animals by touching/eating bc of poison or prickles like ...
-(built) "salt-evaporator" (maybe an addon to water purifier)
-Salt can be used to conservate your meal if decay comes into play or just for better taste plus gives more energy. Multiple abilites, if research and/or disease joins the game.
-plastic and other stuff from pollution (by finding them you get new blueprints), but graduate them into common, uncommon and rare items.
Keep in mind, that supporting environment is a good and necessary matter and additionally for good reputation.
Maybe our rafts switch to the biggest oceancleaner world has seen.
-Ooze (earth for trees, color for paint wood, ...)
-Eggs (cooking, getting animals)
-grains and seeds (food for animals, planting)
-some sort of fabric (carpet, blanket if its getting cold and coldness makes damage to your health)
-Algae (food, paint, making paper, wallpaper)
-bones and gristle (for building, deco or go shaman ways *smirk*)
-(built) Rake (for treating the earth after harvesting rare trees)
-(built) brush (painting, cooking)
-flowers (healing, cooking, flavour)
-unknown items for identification, additionally ...
-funny recordings/videos when researching new stuff, for instance cooking some unknown stuff (mushrooms) or drinking from a found bottle (Alkohol). While beeing poisened, you are talking with the shark lying next to you on a beachchair holding a Cocktail.