You have seen a tardigrade with the naked eye (without microscope), that's as large as a spot on a ladybug?

No, sorry if that wasn't clear, I've not identified one by eye without a scope. Maybe your fine vision is better than mine, but all the tiniest things in a drop of water are just about indistinguishable without magnification. The kinds of water that have sufficient density to contain a tardigrade just look like they're full of grit, I don't think you could identify which speck was a tardigrade and which was just dirt.

Nymphs are larger (that's why they call them "macro" invertebrates), but it's always good to have at least a magnifying glass if not a loupe or microscope on site.