From "The New Tea Lover's Treasury" by James Norwood Pratt:
The Chinese distinguish five stages of tea water as the boiling point is approached: "shrimp eyes," the first tiny bubbles that start to appear on the surface of the kettle water, "crab eyes," the secondary, larger bubbles, then "fish eyes," followed by "rope of pearls," and finally "raging torrent." Green teas require fish eyes or cooler ...
The old saying goes that "a watched pot never boils," but that simply isn't so. And a good thing, too, for how else can one be sure one is reaching those five stages of tea water? Here's what I think the stages look like:
Rope of pearls
I'm still considering getting that electric tea kettle favored by so many of you, but I have to say, for observing the water stages, nothing really beats a simple glass tea kettle!