The 501 Flow is a self-contained vehicle designed to quickly and effectively study small to moderately sized lakes by "flying" underwater at various depths taking measurements with multiple sensors. The Flow oscillates vertically, like a sinusoidal function, while towed from a moving boat. As such, it measures an entire transect of the water column giving substantially more information than profiling devices which drop and rise vertically without any horizontal motion. The 501 Flow may be easily deployed with no winch.