Safety
Burble
The turbulent low-pressure pocket of air directly behind a moving boat's transom where exhaust and carbon monoxide collect.
The burble is the spot directly behind the boat where the airstream breaks up into a swirling low-pressure pocket. Because air pressure there is low, the boat draws exhaust into it, so carbon monoxide accumulates in the burble, exactly where a wakesurfer riding close to the transom puts their head. This is the mechanism behind most CO poisoning in towed watersports.
Understanding the burble explains why staying out of the immediate stern airstream, using fresh-air exhaust, and never teak surfing all matter so much for rider safety.