Schools and educators who live near large bodies of water can take children out to the shore and have them collect different marine life to set up in an aquarium habitat. The children can observe this marine life in its typical routine environment and use microscopes to get a closer look at the micro-organisms that live in the water. They can collect mollusks and plant-life and watch how these react to outside stimuli, such as new creatures added to the environment and how light affects their habits.
A good experiment that teaches children about saltwater environments is raising brine shrimp. These tiny organisms will help students understand how to determine the optimum environment of salinity in which the creatures thrive best. Have the children examine the tiny shrimp eggs through microscopes first; then based on their observations, they can create different salt and water environments and see which one provides the right saline levels to successfully raise and hatch their organisms. Have students make careful notes on their water to salt ratios so they are able to present their findings to the class.
Raising a small frog, from embryo to full maturity, will demonstrate the life cycle vividly to students with a frog hatchery. These are often set up inside of a glass aquarium or ventilated plastic tank to recreate a marsh-like environment in which to raise most species of frog. Some science supply manufacturers offer kits with all the items needed for students to arrange and build a habitat of water and rocks where they can watch the embryos through magnifiers and track their progress as they turn into tadpoles. The students will feed and care for the tadpoles, keep the water at the correct temperatures and make sure there is the right amount of light and easy access to the water so the tadpoles can successfully turn into full-grown frogs.
Another experiment that brings hands-on interaction to students is how penguins and whales survive in freezing cold water and extreme climates. Have each child place one hand in a plastic bag then stick that hand into another bag filled with vegetable shortening. This simulates a layer of blubber that acts as insulation around the skin. Have each child put the other hand into another plastic bag then have them place both hands into a bucket of ice cold water. They will feel how blubber helps keep mammals warm as the hand without the shortening will become colder than the insulated one over time.