National Geographic : 1948 Feb
Sledlike Craft Push Air to Speed Through Water Only Inches Deep Appropriate to the sky-and-water landscape of Hillsboro Marsh are ingenious air boats. Old auto engines turning airplane propellers drive the flat-bottomed boats. Screening prevents injury from whirling blades. a nationalal ueograplmc Society Kodachrolles by Willard I. Culver An Air Boat Roars Faster over Grassy Shallows than Across Open Water Grass and reeds, leveled by its passage, provide a slippery "runway" and reduce water drag. Skimming over such shoals the craft may speed at 50 miles an hour. Big rudder, deflecting the slipstream, is plywood.