2 Peter 2:13

13 suffering wrong as the wages of doing wrong. They count it a pleasure to revel in the daytime. They are stains and blemishes, reveling in their deceptions, as they carouse with you,

Typically, sinners will commit their wickedness in the night time in order to cover their sins. But these false teachers were so consumed with their lusts that they boldly sinned during the day where all could see them. They reveled in their deceptions (they made a party out of it). And they also mixed with the church in their meetings and even their worship services (and I suppose they tried to appear as believers in order to deceive them and later to bring them into adultery with them, v. 14).