Sea Jerky consists of dried fish skins. It comes in different sizes and is sold by various companies. It is very hard and crunchy so is sometimes labelled as a dental treat. I don't know if it actually does clean teeth. One other advantage is that the treat is low calorie so might be useful for dogs with a tendency to gain weight. Nutritionally it is said to contain the the usual omega oils associated with fish.
I have given sea jerky for some years with no issues. However, I recently bought a size that was slightly larger than usual. Two of my dogs have been ok with these but my youngest is smaller with a correspondingly smaller mouth and teeth. The other night she did not chomp the cube properly and some of the pieces got stuck in her throat. Eventually she cleared her throat but I am not risking it again and have passed the remainder on to friends who have larger dogs.
It's a good treat but I would advise pet owners to be sure to purchase the correct size for the dog.