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.
Tell your parents and report it to the police.