Pictured here are two eggs cases belonging to a blotchy swell shark (Cephaloscyllium umbratile) or nanuka-zame (ナヌカザメ) in Japanese.
It's basically a catshark that can puff itself up as a means of self-defence.
I haven't seen any of these sharks, but we found these two egg cases relatively deep, at about 23 metres...where white against a primarily brown background was a dead giveaway. Having them deposited so closely together is rare according to my dive guides.
The eggs are relatively new, and it takes about 10 months for the babies to mature and hatch...which means that these egg cases should be around until early next year. Within a short time, all the guides in the area will know about these eggs, so a lot of divers will have the opportunity to see and photograph them (plus keep an eye on them).
If I get a chance to visit again during the interim, I'll make a point of checking again to see how these young sharks progress.