What is the best airfoil shape for flight in ground effect over water?
There are three considerations for this design:
- Airfoil shape
- Aspect ratio
Airfoil shape: high lift undercambered thick and very forgiving - good idea near the ground Gottingen 436, NACA 4412
Low aspect ratio: lower stall speed, better compression lift from ground effect, more stable in pitch
Anhedralled wings: this actually provides more roll stability in ground effect as the LOWER wing has more lift. Anhdralling also helps "trap" more air underneath the wings for greater lift.
Ground effect designs would be similar for travel over flat land or water. Good info in links provided by @mins and @Juan Jimenez.