i dont read all the post before, but i want let you know my opinion.
i have the 10,5 fish on my nikon d300, but for wake pictures, its for most cases to close. in all the years i have the lens now, i used them maybe 3 times and everytime i tried a lot with it (new perpectives etc.). but in all the years, i only took one good photo with it!
you have to be very close to the pbject with this fish! you need a extra dome port in your waterhousing, which is very expensive too.
the 10,5 is for wakeboard photografie not the best choice. go and spend your money, if not already exist in a 70-200 2,8. this is the must have lens!
the fisheye is if you have everything in the bag already.