Make a Balloon Boat which will power itself across the water.
Balloons, straws, rectangular trays (margarine tubs, curry tubs etc), scissors, white tac (stickier that blu tac), rubber bands. Stickers/Pens to personalise if you wish.
We also used stickers and pens for the children to personalise their own boats.
1. Use your scissors to make a small hole in one end of your container just big enough for your straw to fit through.
2. Cut your straw in half and attach the balloon to one end using a small rubber band and a bit of white tac if necessary to ensure it is secure.
3. Push your straw through the hole in your 'boat' making sure the balloon end is on the inside and the straw should be extended outside by several centimeters.
4. Use your white tac to secure the straw on each side so it is watertight. You could also use Plasticine or similar for this.
5. Blow the balloon up using the straw. You need to put your finger over the end of the straw to prevent the air blowing out before you are ready!
6. Place the boat in the water, let go of the straw and off it goes - our Beavers LOVED this bit :-) The messy bit was when they wanted to keep blowing the balloons up. That got a bit wet and messy!.
Variation: just blow up the balloons and tie them and watch them float more sedately. You could have a race to see who gets them to the otherside.