Unless you have tried photographing porpoises that are often more than half a mile away you might think it easy but it ain't! Firstly you need to find them in your binoculars which have a relatively large field of view and give a pretty clear image similar to the one above.
You then have to switch to your camera then, relocate the porpoise in the much smaller viewfinder which gives a minute field of view and a much worse image more like the one above, especially if a cold northeasterly is making your eyes water! Having got something in the viewfinder which of course dips beneath the waves immediately, you tense yourself ready to shoot as soon as it pops back up again, if it pops back up again!
If it does not you have to repeat the process until with a bit of luck you find the porp in your bin's then manage to quickly relocate in the camera viewfinder and then please!!! it shows again and you shoot in time to get a picture!
It is sometimes possible to spot the gulls chasing the porpoises with the naked eye which cuts out the need to first spot the porpoises with your binoculars if you can use the gulls as a marker for where the porps are among hundreds of acres of often featureless sea.
Anyhow if all goes well and you get something you can crop and adjust the brightness etc and have a reasonable view of something that would have been impossible ten years ago!