Great starter project for little toddlers.
The plans are a little hard to read but it is a great simple project you can build together.

(This is not a babysitter, lifeguard, life saving device please don’t leave your kids unattended in the water)

Here are plans for an awesome little sailboat you could make in a weekend with a few pieces of plywood.
http://www.duckworksbbs.com/plans/jim/catbox/index.htm