Sea serpents?

Are there any sea serpents in lakes, rivers or oceans near where you live? And how did you hear of them if there are? And have you seen them?
When i was little, i was at lake washington and i saw a weird serpent-like thing. It looked like a giant eel/dinosaur thing. Just recently though i looked up what it could have ben. I thought maybe it was waves distorting the water to make fish look weird or something but i found out that there is a sea serpent in there, named willatuk, that could have been what i saw. I dont know if its real or anything but it was really cool