Got (into) translates a Greek participle which indicates an action which took place before that of the main verb ceased (Good News Translation “died down”).

They refers to Peter and Jesus, as Good News Translation makes clear, “They both.”

The text can be rendered either to indicate that the wind stopped because they got into the boat, or simply that it was after they got into the boat that the wind stopped.

The wind ceased or “stopped blowing (hard).”

Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on the Gospel of Matthew. (UBS Handbook Series). New York: UBS, 1988. For this and other handbooks for translators see here .