A freelance Naval Architect, Charles Roring has an interesting site with quite a few articles on various marine subjects. Topics include: Naval Architecture Books, Hydrostatics and Stability, Ship Design, Propeller and Propulsion, Marine Environment and Coral Reef and others.
Some good information here.
A man that has made a life of studying various natural developments noticed years ago that certain whales have odd "bumps" on the leading edge of their fins. He thought that was really odd.
A long story of chopped up whale fins and other oddities led him to discover that these bumps radically change the air/water flow over fins/blades. There is a company using this knowledge to create a fan that moves the same air with a lot less power.
Makes me wonder if there wouldn’t be a good application to boat propellers.