^^I'm not sure how to reply with the quote thing but to landlocked, Alex did a big review on it that is somewhere on wetpixel. if you google his name + nauticam wacp it will come up. I've used it a few times and it is one hell of an optic. It is razor sharp at any focal length, you can shoot it at much wider apertures than normal rectilinears (or even fisheyes) and the ability to use the 28-70mm gives unmatched versatility. It also balances extremely well in the water and is so easy to dive with.
It is definitely an investment, but is worth it IMO. I shoot the RS13mm which is an amazing lens and I was skeptical the wacp would match it in terms of sharpness and IQ but to my eye it definitely does and I'd love to complement the 13mm with the wacp but unfortunately I just can't afford to haha.
Almost all the shots I have with it are on external drives but I can post them later. Here is one meh shot but with a 100% crop also so you can get an idea of how insanely sharp it is. (athought wetpixel is crushing the quality, not sure I can do anything about that?)
Nikon D4, Nikon 28-70