Yes, my living room is now filled with a big, cardboard sailboat. We've had a blast with it though! It's pretty simple to make. I cut off about a foot and a half from the bottom of a dishwasher box, and then cut out a shape that looked boat-like to me for the bottom of the boat. Making the sail was a little more complicated, I used a long piece of cardboard and wrapped it into a tall rectangle, and then cut slits in the bottom of the boat and slid the flaps at the bottom of the rectangle into it, and taped it down. I used one of our silk scarves for a sail, and rigged her fancy new steering wheel on a cardboard box. You could make a wheel out of cardboard too though! She's had a lot of fun with this, pretending to fish, asking me for a yellow coat and blue hat (like Little Bear wears in Gone Fishing) and of course, turning the wheel.
This would be great fun for a sailing birthday party =) I drew on the waves, but you could let the kids decorate it with paints or poster markers.