Seal or otter?

Hello everyone,

I've got another question about what we saw in Lincolnshire! At the time, we thought this was an otter because we've never seen a grey seal before. However, we know seals have been seen here and it wasn't diving like otters do, it was just popping its head up and then straight down, not arching its back. Sadly the photos aren't overly clear as it was hundreds of feet away from us! It seems to have a white patch on the left side of its head, probably making it a seal? We never thought we'd see one so we're struggling to believe it and just want a second opinion.

Thanks in advance!