Paddling is a thrilling sport.  You need all of your wits and fast reflexes when dodging rocks and boulders.  There are plenty of fun opportunities when you are on the river.  Drugs or alcohol deaden your senses, slow reaction time, and you really need both when paddling.  We never paddle alone for a good reason, someone in your party may need you to rescue them - it happens.  How would you feel if a close friend died because you couldn't provide assistance due to impairment?  Save the beer and pretzels for your après-boating meeting - dinner perhaps.  This is a great way to blow off steam, look back on the fun you had that day, and cement great friendships.