"which activity could lead to carbon monoxide poisoning?"

Teak surfing is an activity that could lead to carbon monoxide poisoning. It is a water sport (illegal) wherein the person holds onto any part of a powerboat (such as the swim platform, swim deck, swim step, or swim ladder) while being dragged through the water. The boat may create a suction behind it and can trap exhaust fumes behind the boat, which can cause carbon monoxide poisoning to the person holding on to the boat.