For the observation of macroscopic and microscopic life in aquatic and marine environments we treat the animals and algae as phase objects. The combination of a collimated light beam with a spatial filter and a matched filter in the focal planes allow us to image even the most transparent objects. We illustrate the capabilities of our optical designs with three cases: the Schlieren observations of swimming tracks of planktonic animals, the observations in three-dimensions of the swimming behavior of mating copepods, and the observations of planktonic and benthic life in situ. We discuss the basics of our design and suggest further technical developments.

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