I recently purchased the new D5 Mark II Canon camera. My intentions are to replace my current Canon camera with the net D5 for my underwater photography.
Last week I purchased the Canon EF 24mm f/1.4L II USM lens to use in an Ikelite housing with dual DS160 Ikelite strobes.
Over the last few days I have taken lots of images with the new D5 and the new EF 24mm lens. I love the lens and think that I have made a great purchase. The lens will focus as close as about 9 inches which is important in underwater photography.
My images are clear and sharp. Don't kid yourself by "settling" for a cheaper lens as the higher cost is worth the money, assuming the quality of your images are important to you.
I would recommend this lens for any wide angle close focus use in underwater photography.