Most salt water poppers and walking baits will sit tail down, vertical, or even sink at rest. The reason for this is that they are designed to cast longer into gnarlier conditions with heavier gear. As mentioned above, fish don't know the intended use or the salinity of their environment. I use frsh water lures in the salt, and salt water lures in fresh water quite often. When going from salt to fresh, step down the hooks a bit, and vise versa.