Charles Spurgeon Commentary Jude 1:10-12

"But these rail at whatsoever things they know not: and what they understand naturally, like the creatures without reason, in these things are they destroyed. Woe unto them! For they went in the way of Cain, and ran riotously in the error of Balaam for hire, and perished in the gainsaying of Korah. These are they who are hidden rocks in your love-feasts when they feast with you, shepherds that without fear feed themselves; clouds without water, carried along by winds; autumn leaves without fruit, twice dead, plucked up by the roots;" — Jude 1:10-12 (ASV)

But what they know naturally, as brute beasts, in those things they corrupt themselves. Woe to them! For they have gone in the way of Cain, and ran greedily after the error of Balaam for reward, and perished in the gainsaying of Korah. These are spots in your feasts of charity,

You seem to be sailing smoothly along over the placid waters, but these men are like hidden rocks—that is the expression used by the apostle rather than "spots."