This year I helped the children make an ocean in a bottle to take home with them. I used the tutorial at Delicious Mom as a basis for this activity. The materials you will need are a clear plastic bottle (about 16 - 18 oz. in size) for each child, baby oil or mineral oil, sand, seashells, blue and green food coloring, glitter, and a hot glue gun.
This picture doesn't capture how fun the bottles turned out, but you can see the layers of the sand, shells, water, and oil.
I found sturdy water bottles that were the right size, but they had ridges on the sides and it was difficult to see what was inside. Be sure the bottles you use are smooth. I ended up using the bottles the baby oil came in, which were perfect because they had child-proof lids. If you use bottles with regular lids you will need to use a glue gun to glue the lids on the bottles before the children take them home.
I also found I needed to rinse the sand several times before I used it. I had a new bag of play sand but when I put it in a bottle and added water, the water turned muddy. After rinsing the sand with water the small particles washed away and the water was clear. Before class I put clean sand in a bottle for each child, and I mixed together a pitcher of water with one drop of green food coloring and two drops of blue. This water will be too dark so dilute it until you have the color you want. The combination of blue and green will give you a pretty ocean color. I filled several water bottles with this colored water and took those to class.
During class I had the children put a selection of seashells in each of their bottles, and then I helped them pour the blue green water into the bottle, filling it half full. If you have a large class you may need additional help for this activity. After the water I helped the children put a pinch of glitter into the water, just for fun. The final step is to fill the rest of the bottle full with baby or mineral oil. Secure the lid with glue. Once the lid is in place you can tip the bottle. The sand and shells will stay at the bottom, and the water and oil will make waves as you gently roll it.
Before the children took the bottles home I tied a tag on the bottle that said, "I am thankful for water." As you make the ocean bottles with the children you will have the opportunity to talk to them more about water, and have them tell you about a time they visited a beach or played in the water. They are always excited to bring home their very own ocean.