Observe fish in a fish tank. Movement, fins, gills, eyes, mouth, sleeping, eating, interaction with other fish. Note that is living in water.
Alternatively, purchase a whole fish at the market. Observe body structure, color, iridescence, scales, inside mouth, teeth, gills, fin and tail structure. It is possible to cover with a thin layer of paint, and press on paper to make a print. When dry, label the various parts.
Animals have features that help them live in different environments. A fish's body is perfectly suited to life underwater, just as our bodies are suited for life on land.
Fish live under water. Can people live underwater? Why? Then how can fish? We have lungs to breathe air (oxygen), and fish have gills to extract oxygen from water.
We have legs to go places. How do fish get around? Talk about fins and tail movement in water.
Fish are not mammals, so they do not have live babies. They lay eggs. (Show photo).
Have the children draw a large outline of a body and tail on paper. Cut it out and decorate with tissue fins, bright markers and glitter. You can make it 3 dimensional by stapling or taping a backing, and stuff it with bits of newspaper.
Create flying fish for counting games: fill old socks with lima beans or similar, tie it closed with a knot. Throw at a target, or into a container.
Crayon resist: draw colorful fish etc. with crayons; paint over with a thin layer of turquoise watercolor.
Counting sets of goldfish crackers on to paper fish bowls.