I watched this show as a child in North America in the early '90s, though it is probably older, and have nothing but vague memories with which to identify it. Thus, anything fitting even one of the criteria is a likely candidate and would be a helpful clue! (It's also possible that I've somehow combined multiple shows in my head.)
Here are the details I remember:
- Main setting: under water (magical?) kingdom
- Protagonists: small, colorful-haired creatures reminiscent of Trolls (though probably better-looking) One of these was a "Princess" (who may or may not have had blue hair)
- Antagonists: a woman and her two male cronies on a ship; the woman was likely dark haired, tall and thin; one man was tall, the other was short, neither one very bright
- There was also some theme of pollution, i.e. dumping garbage/oil into the water, smoke into the air
This probably isn't much to go on, which is why my previous searches have been fruitless, but any help would be much appreciated!