Bigfoot; yes, just look at Tenacious D!
Nessie; No, has been scientifficly proven not to exist, there is another "seamonster" tough that exists, but let me find the info on that
Possibly only existing "Sea Monster";
I believe this creature was called Ogopogo, a sea-serpent like creature living in like Okanagan(Spelling?) While scientists were trying to find it with an underwater camera, they found sink holes, caverns, etc. etc. where a large creature like this could possible live.
After investigating one of the sink holes further, something attacked and destroyed the camera, after seeing a large snake shaped shadow just underneath it.
Indicating there might be a species of large Sea Snakes still around, we know nothing about, probably survivors of the pre-history, which wouldn't be a surprise since Turtles/Tortoises and Crocodiles also are survivers of these periods.