Alcohol and drugs affect balance, vision, coordination, judgment, and reaction time. Alcohol is a major contributor to vessel accidents and deaths. This is a particular issue with paddlecraft because they are more likely to capsize when persons on board lose their balance.
Specific standards exist for determining when an individual is intoxicated. The standard for operators of recreational vessels being used only for pleasure is a blood alcohol concentration (BAC) of 0.08% or higher.