<div> Studying and monitoring the ocean is a vital part of managing its valuable natural resources effectively and sustainably. Optical and photonic techniques are increasingly being used to better understand the ocean environment. Opening chapters in this book provide an introduction to subsea optics and imaging, while the middle sections look at biogeochemical optics in the environment, including hyperspectral underwater light fields and bioluminescence in the sea and describe subsea imaging and vision, including holographic imaging, photographic, digital and video techniques. The conclusion covers subsea optical metrology and mensuration including optical techniques in studying suspended sediment, turbulence and mixing, raman spectroscopy, lidar systems and operational multiparameter subsea observation platform.</div>