Rats! Every ship had rats and most sailors believed that these rodents who inhabited the dankest, darkest parts of the ship knew when misfortune was about to strike. If rats scurried off a ship at dock before it set sail, the voyage was sure to be doomed.
It was bad luck to kill a turtle and not eat it, but good luck to carry its bones around in your pocket
Storm Petrels, also known as the Birds of our Lady, by the French were believed to be sent by the Virgin Mary to warn ships of coming storms.
Sailors believed Manta Rays could attach themselves to anchors and drag a ship down to Davy Jones' Locker.
From the fiends, that plague thee thus!--
Why look’st thou so?’--With my cross-bow
I shot the ALBATROSS.
And it would work ’em woe:
For all averred, I had killed the bird
That made the breeze to blow.