  Unicellular microscopic organisms living in aqueous environments outnumber
all other creatures on Earth. A large proportion of them are able to
self-propel in fluids with a vast diversity of swimming gaits and motility
patterns. In this paper we present a biophysical survey of the available
experimental data produced to date on the characteristics of motile behaviour
in unicellular microswimmers. We assemble from the available literature
empirical data on the motility of four broad categories of organisms: bacteria
(and archaea), flagellated eukaryotes, spermatozoa and ciliates. Whenever
possible, we gather the following biological, morphological, kinematic and
dynamical parameters: species, geometry and size of the organisms, swimming
speeds, actuation frequencies, actuation amplitudes, number of flagella and
properties of the surrounding fluid. We then organise the data using the
established fluid mechanics principles for propulsion at low Reynolds number.
Specifically, we use theoretical biophysical models for the locomotion of cells
within the same taxonomic groups of organisms as a means of rationalising the
raw material we have assembled, while demonstrating the variability for
organisms of different species within the same group. The material gathered in
our work is an attempt to summarise the available experimental data in the
field, providing a convenient and practical reference point for future studies.
