Semi fish eye, INON UFL-MR13. Lens of spectacular effects. Saga sells with adapters for Nauticam or Isotta designed for the Nikon 60 mm, but also works with another different adapter for the Canon 60 mm.
Optionally, I have a flash of optical fiber, designed by Saga, with adapter for flash Inon Z-240, but also it might adapt to similar others.
New it was costing more than 1000 Euros only the lens. I sell for 590 Euros, the Inon lens plus the 2 adapters Saga.