I'm guessing that your professor isn't very technical or aviation orientated based on the scenerios you get...
My question is not really "is this possible?" though I am interested in that as well. But how would they get water to do this? Is there enough water stored in the tank on the plane to do something like this? How much water is typically in these water tanks?
Thanks again!
As already said, the potable water and lav liquids are stored in tanks that may not be accessible in flight, but you have to assume that one or both are accessible. You also have to assume that the contents of one/both can be routed to the forward cargo compartment (note that every big plane that I know of that's big enough to use on trans-ocean flights has separate front and rear cargo compartments) - this can involve an access panel that can be opened or cutting a hole in the cabin floor with the crash axe. I'm assuming that you aren't given a figure on how much water would be required so I'd just use a "pulled from thin air" amount.
Note also that unless the plane has every seat occupied you could move passengers as far forward as possible to make the plane more nose heavy, including putting some heavier passengers in the cockpit (there are extra seats for people giving check rides to sit in). It's somewhat amazing how much difference a flight attendant walking from the rear to the front of the cabin makes. The same could be done with carry-on bags, even stacking them at the front of the cabin and using belts, neckties, or whatever is available to strap them in place. Some planes also have a tail mounted fuel tank, as you mentioned. Burning fuel from that would also shift the CG forward and lower the nose. Using these options would mean transferring less water to the cargo compartment. All of these steps should be done first in the real world since they are relatively easy compared to improvising a way to get liquids into the forward cargo compartment.
I wouldn't mention it since it seems that the desired outcome is a stable water landing, but water is self-leveling. If the plane is nose up to start with, putting liquids in the forward cargo compartment results in the water being deeper at the aft end of that compartment than at the front initially. But as water is added, the point is reached where the nose of the plane begins to come down. Guess what the water does - flows toward the front of the cargo compartment shifting the weight even more toward the nose. The nose lowers more, the water shifts more, the nose lowers more, keep repeating. So you'd have to add the water to the forward cargo compartment slowly, letting the plane reach a stable attitude before adding a little more. Otherwise, you add a lot of water, the nose goes down too much, you have to take some water out to bring the nose back up, over and over, until you stumble on the correct amount of water.
Jim