Stranded on a desert island: Which 4 would you choose?

[Warpy]

76. Knife, tarp, first aid kit, anything else optional

Knife would allow me to harvest sea grass to turn into twine for tying sticks together for more permanent shelter, weaving a hammock and fishing net. Knife tied on a stick would make a good spear. The tarp would keep me from being broiled to death during midday. Twine, sticks, and dry grass could produce fire. First aid kit would keep small problems from developing into fatal ones.

The problem of course is water. While rainwater could be collected in the tarp, storage would be problematic unless enough coconut shells had been amassed to take care of the problem. If the island is large enough, water can be dug for away from the sea. Now if they'd had a desalinization plant or solar distiller, that would be my fourth item. As it is, I don't have a preference.