Sinking Boat

How do I make a boat so that it floats for 10 seconds, then sink it without touching it, and then bring it to the surface, again without touching it?
- william (age 10)
Victoria, Australia

That is an interesting proposition. I am not sure why you want have something float for 10 seconds then sink, but I have some ideas. If you created a boat with a hole in it, then filled in that hole with something which either disolved in water or melted away, then you would have a boat that would float for a while and then sink. As for a perfect 10 second timing, that is hard to imagine with out more advanced equipment. Best of luck!!!

(published on 10/22/2007)