To make a water sampler, tape nails or fishing weights to the outside of a small bottle to make it heavy. Then twist a screw eye into the top of a cork fitted into the bottle. Tie a sting or nylon cord to the screw eye, and mark it at six inch intervals. Now tie a one foot length of a second string from the screw eye to the neck of the bottle, letting the loop of the string hang loose. Insert the cork just tightly enough to stay in place when the bottle is lifted by the first string.

Carefully lower the bottle into the water to a depth from which a sample is to be obtained. Next, jerk the string to remove the cork from the bottle, wait for the bubbles to stop rising to the surface, then pull up the bottle.

Pour some of the sample into a baby food jar, and label it in terms of location and depth. Obtain water samples from different depths with a water sampler. Compare the various samples with others obtained at different depths and locations.

The samples can be classified by color or cloudiness by placing them next to each other and viewing them from the side against an area of clear blue sky or by using a cloudiness indicator. Look carefully for differences in shades and colors.