We had ours aboard at 6 months and 2 1/2 respectively, the baby in the cabin or carried, the toddler in LJ with line attached to allow a wander without going overboard, and watched of course. On and off over their growing up they were afloat, and apart from Dave doing handsprings along the roof of a narrow boat as we returned to base it was all conducted unalarmingly. I am working on darling daughter to get the baby grandson afloat, but first we buy him a LJ and put it on a line.