If you are interested in learning more the many different types and varieties of seaweed, I have some suggested reading titles for you. Both have been excellent sources for me and feature gorgeous underwater photography.
Seaweeds of the Pacific Coast: Common Marine Algae from Alaska to Baja Californiaby Jennifer Mondragon and Jeff Mondragon is an excellent field guide whether your are an amateur nature lover, like me, or a professional marine biologist. The authors reside in Juneau, Alaska and own an underwater science, wildlife and natural history stock photography business.
Pacific Seaweedsby Louis Druehl, a marine botanist, covers over 100 common species of seaweeds that occur along the Pacific coastline from southwest Alaska to central California. Filled with extensive line drawings and vivid color photographs, this easy-to-use reference covers information on species identification, seaweed biology, the scientists who study seaweeds worldwide, and the essential and sometimes surprising role seaweed plays in the marine ecosystem and our every day lives.