Set up a Pre-K science area that can help your students explore how and why boats float. Cover your table in plastic and set out a container of water. Prepare a basket of boats for your science area that include different size plastic boats. Modify a few boats by attaching heavy magnets on the boat or cutting a slit in the bottom. Beside your water container and boat, set out two empty containers. Label one "Floats" and the other "Not." Before your students experiment with the boats to see which will float, ask them to examine the boats carefully and predict which ones will not float. Students can explore this boat theme idea in pairs and discuss why the boats did or did not float.
Discuss with your pre-k class how wind affects sailboats. Create sails with your class by letting everyone decorate their own 4-inch triangle made of fabric. Punch holes in the top and bottom of each sail and slide a plastic straw through the holes as a mast for each sail. At your science area, prepare an aluminum foil boat with a holder for the straw. Ask your students to go in pairs to the science center and attach a straw to the boat and set the boat in the container of water. Ask one student to count the numbers of breaths it takes their partner to blow their sailboat to the other side. The students can then trade places and let the other person blow their sailboat to the other side. Give them time to experiment on how the winds direction affects the direction of the boat.
After learning about density and water, create a space in your pre-k science area for your students to make their own boat. Supply clay, aluminum foil and cardboard for them to create a boat. Ask them to choose only one and fashion it into their boat shape. They should test it in a tub of water nearby. If it does not float, give them another chance to fix their boat or choose another material. If it does float, ask them to carefully count how many pennies it will hold before it starts to sink. Ask them to remember that number to compare with their classmates to see if their boat can hold the most weight.