Young children can pick up ideas, good and bad, very easily, and an early traumatic experience can set off a life-long fear. If the experience happened when the child was young enough, it might be forgotten, or pushed out of their mind, with the fear still remaining.
I have first-hand knowledge of this. I saw a really horrible thing when I was nearly 5, and ever afterwards I was afraid of
the thing, even though I forgot the original incident. Perhaps my little mind couldn't cope with the awful memory.
Anyway, I had this minor phobia and then suddenly, as an adult, I remembered the horrible incident. It didn't stop the fear but at least I knew where it came from!
So... a fear of big sailing ships might have come from some long-forgotten childhood trauma. Someone might have read you a slightly frightening story from a well-illustrated book, which would give a visual association of the ships and a feeling of fear. You might even have caught a bit of a scary TV programme about tempests or shipwrecks. It doesn't have to be any more dramatic than that for a small child.
I bet if you were hypnotised, it'd all come back to you. Or in time, when your subconscious thinks you're ready, the memory may surface of its own accord.
In fact, if you can ask your parents they'll probably have an idea about what happened.
Much as I love the
weirdness of life, I don't think phobias come from anywhere except our own minds, with a little help from the environment.