So, I played four times.
Game One: I chopped down the tree, and made the raft square before rebuilding the tree. The shark attacks, and the female fights it. She falls in the water, and both she and the shark disappear. I continue playing with just the male, but I begin struggling to keep up with his hunger and construction fairly quickly. He starves to death.
Game Two: I chop down the tree, and again make the raft a full square. The shark attacks, and I'm able to fight it off a few times, getting a fairly comfortable raft with two chests and three trees growing at once. Suddenly, the girl falls in, and I try to get the guy to rescue her, but she dies. This is where the bugs really start happening. I notice here that he stops following commands. He'll build a tree, but he won't repair raft parts, and sometimes won't build things or cook food. He also gets stuck on the fire pit until he gets hungry. I press Restart.
Game Three: This time, the first thing I do is build a chest, then rebuild the tree, and they put all the fruit directly into the chest, as predicted. No more seagull problems, good. From here, I start expanding the raft. I get the raft fairly big, and I notice that the chest is apparently full, as they're not putting fruit in it, so I start making another row of raft to put the chests side-by-side. In the middle of construction, the shark attacks, and the guy fights it this time. He falls in, and I send the girl to save him. She fights off the shark, but he drowns, apparently, because I can't get him out of the water. So I'm left with just the girl. I'm doing alright, since I was already well-off before the guy died, but she too stops listening to some of my commands. The shark attacks the new chest, and she fights it off. I tell her to repair it, and she ignores it, opting to resume building the tree. After she's done, she still doesn't fix the raft. Instead, she starts moving food from the undamaged chest to the damaged one, with the Repair symbol over it. The chests both become full, so I build a third one. The shark attacks the raft where the fire pit is, and she fights it off. I tell her again to repair the two damaged spots, and she plays around with the food some more until I rapidly click the repair button on the fire pit. Finally, she goes to fix it. It's another several minutes, and more playing with the fruit, before she finally repairs the raft under the chest. She, too, starts getting stuck on the fire pit, until she gets hungry. She fights the shark, falls in the water, and I frantically try to make her climb out, but she dies.
Game Four: I start off the same way as Game Three, having decided it is the most effective method. It's not long before the shark attacks, and the girl falls into the water. The guy fights off the shark, the girl is still alive, and I click on her in attempt to pull her out, but she's still acting as though the shark is eating her. She dies. I quit.
Now, I don't know if it's part of the game design to not be able to rescue the other person, but I think it's a feature that should be available. Also, as you may have noticed, the people seem unable, or unwilling to repair parts of the raft that are under chests, and ignore some commands after one person has died. I would also like the option to have both people fight the shark.