There are reportedly 84 identified species of sponge1 in Hawaiian waters, and likely many more undiscovered. Identifying sponges properly is beyond the realm of the casual diver. But even so, they are worth noting, their colors and shapes add a great deal to the interest of the reef...
1) Hawai'i's Sea Creatures, A Guide to Hawai'i's Invertebrates, John Hoover, Mutual Publishing, 1999