a whitewater kayak or canoe move that involves lifting the bow of the boat to get over an obstacle.
The word is an onomatopoeia to describe the sound of the boat hitting the water when the move is performed correctly. The boat lands flat on it's hull, making the "boof" sound.
That drop is shallow, so you want to boof it to avoid hitting bottom.
The best line is to boof that rock so you don't get stuck in the flow going the other way towards that nasty bit.