It is generally believed that in order to generate waves, a small object (like an
insect) moving at the air-water surface must exceed the minimum wave speed (about 23
centimeters per second). We show that this result is only valid for a rectilinear
uniform motion, an assumption often overlooked in the literature. In the case of a
steady circular motion (a situation of particular importance for the study of
whirligig beetles), we demonstrate that no such velocity threshold exists and that
even at small velocities a finite wave drag is experienced by the object. This wave
drag originates from the emission of a spiral-like wave pattern. The results
presented should be important for a better understanding of the propulsion of
water-walking insects. For example, it would be very interesting to know if
whirligig beetles can take advantage of such spirals for echolocation purposes.

References:

Capillary-Gravity Waves Generated by a Slow Moving Object
A. D. Chepelianskii,  F. Chevy, E. RaphaÎl
Physical Review Letters, 100 (2008) 074504-(1-4)

Wave drag on floating bodies
M. Le Merrer, C. Clanet, D. QuÈrÈ, E. RaphaÎl, F. Chevy
PNAS, 108 (2011) 15064-15068

Capillary-Based Static Self-Assembly in Higher Organisms
J. Voise, M. Schindler, J. Casas, E. RaphaÎl
J. R. Soc. Interface, 8 (2011) 1357-13