I'd spent a couple of days camping on Mull in August 2016 and managed to get some quite long distance shots of two otters - mother and cub - hauled out on a rock to eat their fish.
I was very keen to get back there and got another opportunity in November of the same year. I soon realised that a 300mm lens, even with a 1.4x converter, wasn't quite enough for good pictures of sea eagles. They see you creeping up on them, and fly off before you're in range!
I was very fortunate, however, to see a sea eagle swoop and catch a fish. If only I'd had my 150-600mm Sigma Sport then!