This varicose phyllidia is a small nudibranch, which I saw several times over the course of a week or so. Apart from being a lot smaller than the clumpy nudibranchs I saw a couple of months back, the varicose phyllidia has gills under the mantle skirt rather than in an exposed, wavy clump.
This one was two to three inches long. In the middle photo, the tiny white-spotted toby and small brown surgeonfish give a sense of scale.
I saw this little ambon toby in the shallows one day. The lines radiating from the eyes are quite distinctive. Supposedly they can be skittish and hard to approach, but this one seemed unperturbed by my presence.
Hawaiian whitespotted tobies are small pufferfish, under 4 inches long. The one in the top photo is a female, probably looking for a spot to deposit her eggs. The toby following her (second photo) is a male. After she’s deposited her eggs he’ll fertilize them. Neither will stay with the eggs.
A couple of days after taking this photo, I was in a different location when another pair of these tobies zipped up to me and went by a foot away. In that case, it was two males, the one vigorously defending its territory from the interloper.
In my attempts to identify what I see in the water, I use John P. Hoover’s book The Ultimate Guide to Hawaiian Reef Fishes, Sea Turtles, Dolphins, Whales, and Seals. His website is hawaiisfishes.com.