The 10-17mm has been a favourite of mine for a while now - so I really have a lot of images from it that I like. For those who want to read a bit, here is a link to an article on my website.
Like any 180 degree full frame fisheye the 10-17mm at 10mm is an ideal UW wide angle lens. Excellent for close focus wide angle, wide scenics, reef scenes and diver + scenery shots:
Here is a typical CFWA:

And a bigger scenic:

It can be hard to create space underwater, while still being close enough to a subject to get good colour, contrast and clarity. The 10mm end of the 10-17mm is ideal for this:

Same lens, same subject, excellent flexibility:

To be able to take both of these shots while still in the camera to subject distance sweet-spot for the lens (i.e. not having to back off too far) is awesome.
Perhaps the greatest benefit of the zoom is that it turns the fisheye into a great big creature lens. The 10.5mm is often just a bit too wide - and can be frustrating is subjects don't come close enough. Being able to zoom in a bit helps fill the frame giving the portrait more impact. It also lessens the tadpole effect (big head, tiny body) that you get with the 10.5mm (or just the 10mm end) when the subject does come right up to the camera. And you have the flexibility of being able to zoom either way as you need.
This one is a little bit tadpoley, but not too bad.

Big creature, frame filled.

Sharks can easily tapdpole with fisheyes, but the 10-17mm at around 13-15mm just seems so ideal for these subjects:

And finally, as long as you can get close, the close focusing allows you to shoot small to medium sized subjects:

which is particularly useful in low viz areas, like here in the UK:

Alex