I'm reaching the conclusion that Nessie exists, but Scotland doesn't. And that people are way too hung up on language. Language doesn't exist by itself, to be discovered by humans, the way physics does. Language is made by humans, and we remake it a little every time we speak or write. Loch Ness is both a loch and a lake at the same time. Which term we use depends on context. If you're asked what you sailed on yesterday, the proper answer would be Loch Ness. If you're asked what those bodies of water in Scotland are called, the proper answer would be lochs. If you're conducting a biology experiment that requires samples of microscopic life from the bottom of every lake in Europe you wouldn't skip Loch Ness because "it's a loch, not a lake".
What something is isn't the same as what something's called. You could call it the Sea of Ness or the Nessian Microocean or Queen Mary's Puddle or Burn's Spittoon and it's still the same damn body of water. Whether other people will know what the heck you're talking about is another matter, which is why we have language in the first place.