Abstract: A float having symmetrical fore-aft and port-starboard cross sectional surfaces in the shape of multiple, above- and below-centerline, ellipsoids is hydrodynamically-contoured to support suspended devices, typically a seismic air cannon, at even height/depth in the water, and at even attitude (roll, pitch and yaw). The float places nearly constant force on the tow line over a broad range of tow speeds from at least 3 to 12 knots during sea states from 0 to 6 and in the presence of variable direction surface winds to 25 knots. The float transitions easily and smoothly from displacement to hydroplaning operational modes, permitting that seismic equipment may be towed smoothly and at even depth in the water even at high speeds, thus accelerating seismic surveys. The preferred fore-to-aft contour of the lower surface is in the substantial shape of an ellipsoidal surface of from 4-10 feet, and most commonly 7 feet, in length with a height of from 6-14 inches, and most commonly 10 inches.