12 blemishes. The Greek word translated “blemishes” usually means “rocks” or “hidden reefs,” which are a danger to ships. If Jude is making a play on words, it is to the effect that teachers are “dangerous, rocky blemishes” in what should be calm waters.
feast with you without fear. The false teachers may have made the love feasts occasions for blatant immorality. Even apart from this their presence at the meals would have been a concern to Jude. Because teaching took place at the love feasts (Acts 20:7, 11), there was opportunity for the false teachers to advance their ideas.
waterless clouds. A metaphor for a form of hypocrisy that fails to produce what is promised (2 Pet. 2:17 note).