This game is awesome. my few ideas are: range, perhaps a flimsy bow with crafted arrow, all the way up to a mounted ballista because.... pesky shark. I would love some kind of breeding in farming to get better food, fishing tiers and bait would be great.
Oh and also: reinforced foundation, i imagine a foundation surrounded my metal, takes three shark attacks to "kill" mabye you need a ballon to keep it afloat.