Air Funnel

The problem I've had with filling bottles full of water or other liquids is that a funnel causes splash back as air attempts to escape through the same opening as the water is poured into.

This funnel attempts to solve that problem by creating a separate channel for which the air can escape.

The air escapes through a separate opening that drains into the funnel (so splash-back is contained in the funnel), and is designed so if you overfill the funnel water shouldn't splash out.