When we were down recently our guide made us ceviche after a morning of fishing. He basically chopped up the fish, rinsed it in salt water, squeezed the juice from two fresh limes on it and while that marinated he chopped the vegetables. He said it would be marinated by the time he was done chopping. He chopped a couple of tomatoes, white onions, and a good bit of fresh cilantro. Salt, pepper and some Marie Sharp's to taste. Done.
I think however the freshly caught fish, salt air and scenery might be the key ingredients. :~)
Good luck, worth a try!
Hey, how about that ceviche at BB....my husband loved it there!!