High Performance Under Water Sail - PowerNet - Butterfly R-3-A
Part of Dark Sky's ElectroFish project was an effort to maximize the Cd of traditional sails.
This version was too complex for OpenFoam's SnappyHexMesh to analyze, but it was the early data showed it would achieve a Cd of 2.5+. A parachute is only 1.4.
The paper is under review for publication, the draft is available here