it's not what you'd think. I'd stick as close to the waterfall as I could: erosion over time is going to create the deepest spot, and if you are free climbing, if things go south you jump into the waterfall instead of taking one shit of a tumble.
with a waterfall like that, right around it is at least 20 ft deep, which is easily enough. 1:10 ratio for safety; plus since you'd land in a dive instead of a cannonball you can project momentum horizontal if needed. There's also the ability to flip and use that momentum to turn upwards. Diving is an art; and if you're wandering around across vast areas, one of the best tools in your arsenal.
does that count?
you throw it once and it hits someone, depending on where you hit them more or less damage is dealt
its a big shallow area