Zoom into the horizon with C: springy zoom, scroll up to 64x, steady aim, far mobs that stay visible and a rangefinder. Client-side.
The horizon, up close.
The camp on the far shore springs into view, with the magnification and rangefinder under the crosshair.
Scrolling in on a creeper 115 blocks away, just as it goes off.
A village 240 blocks away.