The Monterey Bay Aquarium Research Institute (MBARI) is a nonprofit oceanographic research centre that has set up a live stream of audio from a hydrophone set up at 900 metres below the ocean’s surface just outside Monterey Bay, California. You can tune in to an (almost) live stream anytime at the YouTub stream below:
MBARI also have a bunch of sample recordings posted up with some really interesting examples of calls from whales, dolphins, etc. Some of the whale sounds you really need a subwoofer or good headphones to be able to hear properly. Check them out at: