Our oceans are not quiet places, with underwater sound playing a dominant role in the lives of marine fauna. Invertebrates snap and stridulate, fish grunt, honk, trumpet or blare out the same sound incessantly, whales whistle, groan, click, sing melodies, or for some species, blast prey with concussive impulse signals. The range at which some biological signals travel can be extraordinary, for example a duct in the deep ocean north of the polar convergence zones allows energy in the frequency band 10-120 Hz to travel 1000's of km without losing energy apart from radiating into an expanding cylindrical space. Acoustic navigation cues prevail, fish choruses are routinely detected at many tens km, wave breaking noise has been detected at hundreds of km while recognisable great whales signals may be detectable at 150-200 km in the deep ocean, expanding the definition of what is a "group" considerably. The diverse use of sound by marine animals, the biological adaptations marine fauna have for creating and receiving sound, the propensity of humans to make loads of noise in the ocean, the complex physics of ocean acoustics, engineering challenges of collecting sounds useful for analysis plus a required expertise in signal processing, has led to a challenging, fascinating, diverse and rewarding career, some of which will be enumerated here. While we have come a long way in understanding biological underwater acoustics there is an awful long way to go with many more careers of rewarding science ahead.