Rain Cloud

It cancels fall damage, so one layer at the base of a shaft turns a hellevator into a one-way express with no potion or accessory involved. That alone is worth hauling a stack down from a floating island.

The falling drops do nothing but look good, and they stop dead against a solid block placed underneath. A hammered block does not stop them. Lower video quality settings cap how many clouds in one area will actually rain, so a large build looks patchy on a weaker machine.

Because these generate under floating islands and floating lakes, that streak of rain in the sky is your landmark. If you are hunting islands by air, look for the drizzle rather than the island itself.