For good results observing pond water place a drop of water taken from your sample source where there is some debris. If you let the sample container sit quietly much of the debris will settle to the bottom of the container and you can get a dropper full and put it on the slide. Place the cover slip on the drop. If there is water coming out from under the coverslip around the edges you can wick it away with a piece of tissue. The water will suspend the organisms and the coverslip will not crush them. The coverslip will keep the slide from drying for a while and as you said, protect the objective from getting wet.

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