Asking the locals where to go to eat is very much a mixed bag. Sometimes they lead you to a place that has a food unique to that area, but may or may not meet your food preferences (see Pittsburgh restaurant putting french fries on everything). Sometimes they lead you to a food unique to that area and it is just a bad idea (see Cincinnati Chili). Sometimes they lead you to a place that was great once, but outgrew its cult status and became a sellout shell of what it used to be (see Big Texan Steak House). 
Sometimes they hit the nail on the head and you find a great spot.
Walking into King Seafood is not all that impressive. Two picnic tables out front, a fresh fish counter facing the door, a looooooong counter running the length of the rectangular building, and a cashier at the end of the counter.
A closer look reveals some wonderful things. First, the restaurant is spotless. There is no smell of fish whatsoever, and the hood above the grill and fryer is so shiny it creates a glare. These are rare traits for any restaurant, much less a small local restaurant in a tiny fishing town. The staff was all very friendly upon entering and was having some lively banter in Spanish with one of their obviously regular customers. I took my phone out to take some pictures and the customer looks at me and says "uh oh, Facebook. Facebook." I gave him the thumbs up and went about my business. He waves me to come over and points at his plate. On his plate was some delicious looking yellow rice and humongous shrimp in some tasty looking and aromatic spices. He picks up one of the shrimp and tells me to try it, then picks up a Yucca Fry and offers that to me as well. I obliged and tried both. Wonderful.
At this point, you can be pretty confident the food is gonna rock. A local gives you the food off his plate and it does not let you down. Order fearlessly my friends, as we will be happy munchers.
Of course, fish tacos are on the menu and I wouldn't be able to sleep if I didn't give 'em a whirl. 
First, though, we had to look at some other food as well. Altogether, myself, Rip, and Rachel ordered Blackened Fish Tacos, Fried Fish Tacos, Mahi Sandwich, Calamari, Fish Soup, Yellow Rice with Fish, Cole Slaw, and 3 sodas. All of this freshness and deliciousness for $60 including tip! Pretty good value.Calamari - light and tender. Yellow Rice - aromatic, flavorful, and fresh. Fish soup and Mahi Sandwich got rave reviews from Rip and Rachel (I could not consume due to pork being in the soup and too much food in front of me to try the sandwich).
Now on to the fish tacos. A well documented fact that I prefer grilled or blackened fish over fried fish on fish tacos. The one exception is if you are using a flour shell and use a very juicy fish. In this case, I find that for a variety of textures, you will definitely need to go with fried fish or (strangely enough) overcook the fish to give it some body. Of course, if you wanted to use a tender fish, why overcook it?
So King Seafood uses flour shells. They do something I have not seen since I left Adobe Gilas all those years ago. They put the shell on the griddle and put shredded cheddar on the shell to melt it. Creates an experience all its own and that is what made me an Adobe Gila's taco addict. 
As for the fish itself, we ordered one order with blackened fish and one with fried. This way, we were able to try both ways and judge what we thought of them. The blackened mahi was plentiful, and cooking on the griddle, made my mouth water. The fish, when fully cooked, was added to the shell and topped with fresh tomato and lettuce. It was then rolled and placed on the plate with sour cream, cole slaw, and pico, with two lime wedges on top. A beautiful presentation and a dish I couldn't wait to sink my teeth into. 
the flavors were delicious after a little pico and tabasco was added. I prefer Cholula or Pickapeppa, but that's just me. Overall, a great fish taco and unique in the ways that it did not contain cabbage on the taco and the rolling of it made it difficult to add more ingredients to it. A fish taco worth checking out. The staff checked with us several times that we were happy and was very gracious. Nice folks. The food was spectacular as a whole and with people that friendly behind the counter, I can definitely see myself going back.
So we amble off with a light buzz and full bellies. We get back to the homestead to find the sun going down. A few obligatory pics to show off that not only did we have a great meal in Marathon Key, but nature took pretty good care of us too. Cheers!
