Here i sit in Tarpon Bay, Key Largo, arrived at 5pm, set the hook in 12 ft, 75 ft rode out, set the alarm, RayMarine RL80 C, for 300 ft drift, had a nap, alarm goes off, WTF...up I leap..boat is doing 3.5kts over land, then does a 180 and back to the other side of the bay, about a mile...finally after an hour comes back "close" to where we set the hook, the boat has not moved at all. This to me proves the inadequacy of today's technology, it just cannot be trusted in it's entirety. Use it, but keep your eyes and senses foremost.