They have a procession around parts of the island like a carnival, celebrating Easter. That's why most of floats have a religious theme, and I think there's a contest that votes for the best float.

These processions are quite a big thing in many Mediterranean villages around Easter and May and can attract a lot of crowds.

The ferry from Naples to Procida was around €30+ return, to Capri was €40-50 which I thought was a bit too expensive for a day trip, plus I heard Capri is also more expensive overall. Not too surprising given how famous it is