Acousticians at the Woods Hole Oceanographic Institution have discovered a way to count all the fish – and zooplankton—in the sea. This seemingly impossible task is made possible by broadband acoustics, or sound waves. While aboard a research cruise on the R/V Armstrong, they test out the ship’s new EK-80 “echo-sounder” which operates at powerful low and high frequencies, while other instruments (the Video Plankton Recorder, the MOCNESS plankton net, and a traditional fishing trawl) are used to ground-truth their findings. Featuring interviews with WHOI scientists Tim Stanton, Andone Lavery, Gareth Lawson, and NOAA Fisheries biologist Mike Jech that explore the benefits of the echo-sounder survey to biological research.