A few forum members have asked me about spearfishing from a jetski. I've been fishing with rod and line from a ski for 5 years, but I'm a novice spearo/freediver.
I've flirted with diving from the ski in the past, mainly doing scallop dives in Whangarei Harbour. Recently, I've been venturing further afield for cray dives and spearfishing.
I've spent quite a lot of time thinking about how I carry my gear and rigging the ski for diving.
In short, I wouldn't recommend a jetski for this kind of activity. Anchoring is an absolute pain in the arse and gear storage options are very limited. That said, it can be done. If you have a ski already, give it a go and see how it works for you, but I wouldn't buy one with this purpose in mind. I can see the attraction, jetskis make awesome rod and line fishing platforms within their limitations, but diving is a different sport. A boat, any boat would be a better option in my opinion.