Make the shark less darn annoying!
The problem is the shark is a completely silent, noiseless predator, and with an expanding base that might incorporate walls there is so way of predicting if the very floor you're standing on is being mauled by a shark. The shark doesn't feel threatening, it just irritates the player.
A suggestion would be to make a barrier of scrap and nails. This can be crafted fairly cheaply and will provide extra resistance to survive at least 1 shark attack. This can help solve the problem of the build up of scrap I seem to have too. Barriers could be attatched to the sides of foundations, and can make loud denting sounds when a shark is trying to eat it.
Just my thoughts :-)