Hawaiian whitespotted toby
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 (right) 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.