[grkvlt]

> To extend this conclusion from the dead fish experiments to mechanical devices, and to demonstrate the applicability of these results in an engineering context, we also show that a flexibly mounted two-dimensional rigid foil, through fluid-induced motion only, is capable of producing net thrust using a negative mechanical power input, i.e. all the required mechanical power is extracted from the flow.

from the paper, which was published in 2006. and re a downstream comment, they euthanized the fish with a bath of anaesthetic, also in the paper.

[sjducb]

I didn't see that part. If it works with a foil fish then it is possible to have net forward thrust only by extracting the energy from the flow of the water.