That's a little bit more difficult, but not by much. It's still a limited number of simple scenarios: same objects, similar cases to model. I'm sure it could have been done easily via preprocessing. But not having seen it, I couldn't tell you whether or not I agreed that they'd actually used the diffusion equation to model the system.
One key point is that most water waves have a dispersion relation where the phase velocity is roughly twice the group velocity. This means that the individual ripples in a disturbance will travel twice as fast as the disturbance, meaning that waves will travel from the back to the front of the disturbance very quickly. If that does not happen, the waves are wrong (by disturbance I mean a situation where something has perturbed the water for a short time, such as something dropped into the water).
One key point is that most water waves have a dispersion relation where the phase velocity is roughly twice the group velocity. This means that the individual ripples in a disturbance will travel twice as fast as the disturbance, meaning that waves will travel from the back to the front of the disturbance very quickly. If that does not happen, the waves are wrong (by disturbance I mean a situation where something has perturbed the water for a short time, such as something dropped into the water).
If not, I'd suggest cutting down a bit on that "straight line" weed you're smoking, it's addling your brains... 
