Let your beauty be not just the outward adorning of braiding the hair, and of wearing jewels of gold, or of putting on fine clothing;

 Peter has been speaking about the wicked men who were disobedient and corrupt in the days of Noah; they were ultimately destroyed. But in the destruction by the flood eight people--Noah and his wife, his sons Shem, Ham and Japheth, and their wives--were brought to safety in the ark. Immediately the idea of being brought to safety through the water turns Peter's thoughts to Christian baptism, which is also a bringing to safety through the water. What Peter literally says is that baptism is an antitype of Noah and his people in the ark. 