This system was created in a hurry in the hopes that we could get a broad enough frequency coverage to spot bubbles in shallow thin layers during an experiment in Monterey Bay. I worked at building relatively broadband matching networks for a set of transducers with nominal resonant frequencies of 104, 165, 265, 420, 700, and 1100 kHz. The final frequency range was 70 kHz to 1020 kHz with data taken every 10 kHz. So far the data have been somewhat confusing and the system never quite worked as planned but it did provide some unusual looks at the water column and some tantalizing evidence that thin layers of phytoplankton can produce oxygen at such a rate as to cause bubbles to form on detritus in the water. And bubbles, you know, are terrific scatterers of sound.