Could have been a previously caught fish or summer run as suggested above. Something that has happened to me several times over the past years, is that due to fish gyrations after being hooked, the line can develop a half hitch over the fish's snout. (Possibilities increase when using front hooks on diving plugs.) When entangled as such, the fish exhibit virtually no fight and can be brought to shore quite easily. It is not until the fish is quite close that you can even notice the half hitch. If you do notice this situation, check to make sure your drag is not set to tight and be prepared. For if it slips off, all heck can break loose.