PassageMaker has a very good article giving an initial introduction to Beneteau’s hybrid prototype. Built in conjunction with Elco (nothing like 120+ years of electric boat experience), they have modified a Swift Trawler 34 to have a hybrid power train.
Pretty slick. I expect the costs (as they have with cars and other things) will come down and become viable in the next few years. Definitely a technology to watch, in my opinion.