Maqsood Ali, a 37-year-old man of no fixed address, has been jailed for indecent exposure and sexual assault.
He appeared at Brighton magistrates on July 17 two days after exposing himself to two girls, aged 14 and 15, and sexually assaulting a 17-year-old girl on Eastbourne seafront.
He was sentenced to 20 weeks for both incidents, to run consecutively.
DC Tod Stewart said, “Officers acted quickly and arrested him within hours of the offences. He has been rapidly brought to justice.”