For complete coverage of all Hawaii's sea slugs, check out the
SEA SLUGS OF HAWAII WEBSITE
by Cory Pittman and Pauline Fiene
Cory and Pauline have found and photographed hundreds of Hawaiian nudibranchs.
Many are new discoveries, and most are not in any of the books. Check it out!

http://seaslugsofhawaii.com

ALSO check out the new and very active Sea Slugs of Hawaii Facebook group.

Also excellent: Hawai`i section of Scott Johnson's website: http://www.underwaterkwaj.com/nudi/hawaii/hawaii.htm

Keoki Stender's website has lots of Hawai`i opisthobranchs.