Can you solve this problem? You're passively flowing downstream in the middle of a river that has its fastest flow in the middle. Most places along the riverbank are too steep or too vegetated, but suddenly you spot a perfect location for coming ashore a distance y away (measured along the river bank). Note that y can be zero so that you only spot it when you're already drifting past it; or if you're slower still, y can be negative. Now assume your swimming speed is a constant v, while the river's flow is V in the middle and linearly decreasing towards the shore. What angle should you take, as a function of your distance to the shore (x), to reach the desired location using minimum effort (i.e. shortest journey or, equivalently, shortest time)?

Now in reality the river at Esdale can occasionally show a bit of additional complexity (turbulence, and other practical problems...) Thanks for reading this far. I'm happy to report that the problem by now has caught others' attention too. That's cool!