How Do Boats Float?




Cognitive Objective: The student will explain how density and displacement keep a boat afloat. The student will manipulate clay and form it to float like a boat.


Density is weight x volume. Boats can hold a lot of cargo before they will sink. Boats and ships weigh thousands of tons, but they still float. Different objects will float in water. Objects that are more dense that water will sink.

Psychomotor Objective:

The students will manipulate the clay and transport the water. Using pouring, lifting, and molding skills, the children will enhance balance and coordination, as well as exercise fine motor skills.

Affective Objective:

The student will recognize how important it is to only load a boat to capacity.

Advance Organizer:

Show picture or video of large ship. Ask the questions: “How much do you think this boat weighs? If it weighs so much, why doesn’t it sink?”


The students will break into 4 groups. Using tubs of water and a variety of objects, the students will test the buoyancy of different objects. The teacher will monitor and make suggestions as the children list the properties of their different objects. The class will decide how to make a table that shows all of the information they discovered as they experimented with different objects.

The students will predict which objects will float that the teacher produces.

On the board, the teacher will make the students’ list. We should order the objects from the lightest to the heaviest. Then we will note whether the object floated or sank.

Pink bottle
Metal clips
Plastic box


The teacher will ask the students to help clean up the experiment.