So, its been quite a while since i have shot a fisheye, used to use a Sea and Sea 12mm on the Nikonos but it belonged to a friend who sold it 
so its been about 4 years for me.
Got the 10.5 about 10 days ago and finally got the chance to use it today. Its a fun lens that is for sure, but definitely have to have some patience for subjects. Luckily enough there were 6 mantas out and about today which is much better than one. When there is only one at the cleaning station it tends to just sit up top and get cleaned the whole time, too far away for fish eye. When there are a bunch they tend to take turns and swoop down over the divers as they are circling back around for a pass with the cleaner fish.
So, i had the opportunity to get a few shots, lucky me. Fish eye not exactly a big diff than the 12-24 for this subject but still lends a cool angle. Viz not the best as you can tell from the darkish blues but hey it worked.
Here's a couple of examples:
The fact that i have shot fisheye in the past meant i had no trouble with strobe placement or backscatter, (ie pull em quite a way back from the parallel position usually used) but i did have a couple of moments looking in the viewfinder and saying to myself "What is that in the lower corner?? Oops! Thats my fin!"
And hey, i have also discovered its a fine self portrait lens too! Autographed copies of that photo will cost you guys a mere $25 a piece!
Looking forward to using this lens a lot more often, can't wait to try it out in the Yap Caverns on a nice flat day...
Mike
ps settings: single manta f8, 125
double manta f7.1 320
lovely portrait shot overexposed f8, 500
