Setting Sail sounds like a great way to kick off a new school year, especially when you are encouraging the congregation to GO!
Folding paper boats is fun and easy, but they don't float very long. Here are a few other boat building ideas I found that the children could make or the families could make together:
Water bottle boats made from two empty water bottles, cardboard, and duct tape
Cork sailboats made from 3 corks, rubber bands, toothpick, and small fun-foam sail
Additionally, the boat ideas suggested above could be part of a summer splash event (or series of events).
