Seen as you have the 100M2 already you may as well just jump into the deep end, both $$$ wise & ability wise. As Interceptor has said it is not the easiest of cameras to use, not nearly as "user friendly" as say a Canon point and shoot.
I would recommend you shoot on land in full manual just to get a good feel for it and if you can manage this get into a pool and do a few pool sessions with it.
Stay patient and you will get the hang of it.
Spend as much as you can on GOOD strobes. The Inon Z240 or similar. WA needs lots of light power. And the strobes will outlast your camera set-up by a long way.
I would recommend you shoot on land in full manual just to get a good feel for it and if you can manage this get into a pool and do a few pool sessions with it.
Stay patient and you will get the hang of it.
Spend as much as you can on GOOD strobes. The Inon Z240 or similar. WA needs lots of light power. And the strobes will outlast your camera set-up by a long way.