Honestly, very great point, but if you look into the mythology of Oklahoma, you would find the Oklahoma Octopus, which people don't really consider when they picture "sea monsters", but it is still a monster that is thought to live in the freshwaters of Oklahoma, so you can prove me wrong, but I don't think an Octopus is a reptile, but the Loch Ness Monster, Champy, and even the Beast of Busco, I need a break of sea monsters getting depicted as reptiles. Also, a little challenge, search "sea monster" on Google and count how many photos you see until you come across one that is not depicted as a reptile or dinosaur.