Thom Demas examined the photo and helped unravel this marine mystery. "Based on the anchor point and the obvious curvature, it's my opinion that this is the spine of a catfish," said Demas. "After reading the note (written by Alanna) I know it was found in a marine location. That means it is the spine of a gaftopsail catfish or a hardhead catfish. Both are in the same family. The gaftopsail is sometimes called the "crucifix fish" because it has a skull that looks like a crucifix."
Thanks Alanna for sharing your picture - and thanks Thom for your expertise.
This video shows a whoppper of a gaftopsail catfish. You can clearly see the prominent dorsal spine.