You could use a compound light microscope or a stereomicroscope.
You would use a standard micron microscope.
Micro microscopic scope
Euglena live at the surface of the water/pond!
compound light microscope
A compound light microscope.
What instrumentProbably a microscope.
seaweed
A compound microscope would be best if you want to see all the organisms in that drop. A simple microscope would not allow you to see as much.
a pond is smaller
Magnifying / Microscope lens
Antonie van Leeuwenhoek, the inventor of the microscope who went on to extensively study and describe all kinds of microscopic life.
The cast of No Swimming in the Pond - 2014 includes: Alisson Haag as Salma
light microscope
pond water