Basildon Crown Court hears the boy's body remained unburied between April 2025 and August 2026.
Lifeboat commander Jonathan Charnock says he was shocked one of the youngsters was just six.
Southend RNLI warns the outcome could have been very different.
An amended c2c timetable will be in place until further notice.
Operator c2c cancels some services to and from London because of the hot weather.
Police say their investigation in Shoeburyness is being taken "extremely seriously".
Former England midfielder Kieron Dyer is the new Southend United head coach.
Police say the blaze is being treated as a "suspected arson" and investigations were progressing.
Police make 13 arrests and turn 250 people away from Southend-on-Sea as they respond to the event.
