Actual quoten is quite close, but more verbose:

(iii) The waterfowl is assumed to be a rigid and smooth body. The hydrophobic feathers and the local movement of the paddling feet will affect the total drag. It is assumed this effect is consistent in the independent and formation swimming. Therefore, the geometry of the ducks is modelled by simple ellipsoids.

This reminds me when one of my professors from undergrad was lecturing about drag calculations and we looked the example of a goose flying which is, as my professor said, ‘essentially a small UAV…’.

HONK what have you done

quack

And ignore any friction caused by water