OK here are my thoughts.
You can add barrels as an item to collect in the game beyond just getting items from them
then 1 barrel plus 10 scrap = 1 rain catcher
3 barrels plus 50 scrap = 1 Still
25 scrap = 1 pressure cooker
5 beets + 5 water used in a pressure cooker = 1 Sugar
10 Potato + 10 Sugar used in a Still = 1 Alcohol
10 Coconut + 5 Alcohol used in Still = 1 Coconut Rum
Killing the Shark will gain you a Hide
6 Wood + 12 nails = Tanning Tubuse Hide in tanning tub = 1 leather
5 leather + 2 Rope = 1 Backpack (expanded Inventory)
2 leather + 8 nails = 1 Pair of Non Slip Boots (prevents you from slipping off ship when walking on wet deck)
8 Leather = 1 Rain Coat (prevents cold from rain)
After killing your first shark, weather effects then begin to enter the game such as storms etc.
Lowest level storm is simple rain the effect simply being you will become wet and cold requiring you to warm up, and your rain catchers filling up with water
the 2nd level is Thunder Storm which will occasionally shoot lightning bolts at your ship causing damage to the highest levels of it.
the 3rd level is Tropical Storm which will hurl high winds at you causing damage to your ship as well as push you off into the water.
the 4th level is hurricane you will need to have prepared ahead of time for this one as you will be running around your ship replacing parts of your ship as this causes high levels of damage.
You can upgrade your walls and floors to metal by applying 4 scrap and 16 nails
1 Barrel + 20 scrap = Airtight Barrel10 scrap = 1 pipe
1 Airtight Barrel + 4 pipe = 1 Wood Gasifier
20 wood used in a Wood Gasifier = 1 Syngas
50 Scrap = 1 Furnace
1 Syngas + 10 Scrap used in a furnace = 1 Metal Ingot
2 Metal Ingots + 1 Syngas used in furnace = 1 Gear
1 Metal Ingot + 1 Syngas used in furnace = 10 Nails
2 Gears + 2 Rope + 2 Pipes = Pulley
1 spear + 4 scrap = 1 Harpoon
2 Pulley + 10 wood = 1 Harpoon Balista (uses Harpoons as ammo to shoot sharks, let the sharks body float for a moment so that after you kill it you can then use your hook to bring it in and harvest it)
10 Metal Ingot + 10 Syngas used in furnace = 1 Lightning Rod (place on top of ship to prevent lightning from damaging it)
Add whales to the game = if you manage to kill one you will get a lot of food and oil. although attacking a whale will make him go Moby Dick on you.
5 scrap + 1 Syngas used in furnace = 1 metal coil
4 gears + 1 metal coil + 1 oil = 1 hand crank battery
4 metal coil + 10 scrap metal = 1 speaker
4 scrap metal = 1 Antenna
1 Hand crank Battery + 1 speaker + 1 Antenna = 1 Radio (perhaps building a radio triggers a special event in the game)