Your post interests me a lot Will, because my father (a Scot) was brought up in North Shields and took me there when I was about 4 yrs old. I well remember the quayside, and watching the herring boats come in. ("Thou shalt have a fishy "etc!) He and his ancestors right back for centuries (my sister has researched this thoroughly) were master mariners, or North Sea fishermen, or port Customs/Excise officers. He himself swore he has Viking blood in him and his forbears roamed the seas in longships invading Scotland! He was in Air-Sea Rescue for part of the War. He could swim like a fish right up until his death.

I'm seasick if I even watch a film about the sea. I'm sick watching waves. I'm sick on a river. I've inherited this from my Irish mother who also loathed the water. But I can swim.
I do fear the sea, and I think most people should.
As a child I was once taken to the cinema to watch 'The Sea Shall Not Have Them' and felt very sick. I had to shut my eyes for most of it!