This affect is seen almost immediately. Alcohol diminishes judgement and decision-making ability. Peripheral vision, focus, and depth of vision are all impaired by alcohol, making it difficult to judge speed and distance. Alcohol also reduces night vision. Alcohol may cause inner ear disorientation, which can make swimmers swim down, not up to the surface, greatly increasing the risk for drowning.
Alcohol slows reaction time.
This effect is seen almost immediately. Alcohol compounds the affects of the sun, glare, exposure to noise, vibration, wind and other motion typically experienced while boating. Alcohol increases this effect. Alcohol reduces the body's ability to protect against cold, creating a higher risk of hypothermia with its accompanying slowed reactions. Alcohol increases the danger of cardiac arrest by causing irregular heartbeat.