Buoyancy would be a serious problem in a situation like this, and considering we can have rafts that are stories high without it sinking, some realism is subtracted. It would be great if you had to keep the raft afloat by not using irregular shapes and making sure there are no holes to let in water. There should also be some way to get to the ocean floor, be it with a diving bell/cage or whatever seems right. The way we build in the game, it's as if we're on a plain, but really, we're in the middle of the vast sea. Scrap metal has very little use now, so upgrading floors from wood to metal to increase their durability would be a nice touch. Storms would also be a nice touch, as storms on sea can mean death for even the most prepared sailor, a storm would be nice to knock over pillars and have the raft take on water. Last thing- the shark seems massively under-powered. In real life, a bite from a shark would leave clothing ripped and cause bleeding (which attracts sharks), and with very little medical supplies, can cause an infection. Who knows, maybe the only way to cure the infection is to find a certain medicated plant on the ocean floor. These are all suggestions, and I know this might be very hard to do with your small team, but they would definitely make this game a lot better.