"Guide to Sustainable Surfing" by Tony Butt.
This is an excellent book for anyone who wants to maintain the oceans. It explains in depth how our choices of lifestyle, materials, and consumption specifically impact the environment for better or for worse. This book had a strong impact on me, and has inspired me to make changes to ensure that I still have an ocean to play in.
Start reading it for free: http://a.co/9PAvwx3