As early as 5 days
Our son started learning about sailing when he was only 5 days old! Ok, so he wasn't really that into it at that age, but nonetheless we went. We took him with us several times on weekend outings leading up to a Halloween cruise over the course of several days (he was born at the beginning of September). Then we went periodically throughout the winter months when the weather was favorable into the spring and summer months - this was when we still lived in olympia, washington, we have since moved and now keep the boat in NC. So, he's sailed with us the entire time. Now he's nearly 20 months and after moving my father-in-laws boat down the ICW from MD to NC next week (yeah, I'm excited about doing this trip!), we're going on a Memorial Day cruise for several days in NC. A week after that we're taking him along on a bareboat charter out of Tortola in the BVIs! I remember before he was born I wondered about this as well. However, it was actually easier to keep tabs on him when he was only minimally mobile. It's more 'interesting' to have him on board now that he climbs EVERYTHING! ;-) good luck...matt