Dylan Cecil was on holiday when he fell into the water at Burnham-on-Sea in Somerset last Sunday.
He was said to have been trying to get a closer look at the sea when the incident happened.
Coroner Michael Rose said a post-mortem examination showed Dylan drowned.
No members of Dylan's family were present at the short hearing when his inquest was opened in Taunton.
It was adjourned until a date yet to be set.
An inquest into the death of a little boy who fell into the water at Burnham-on-Sea opens today. 4-year-old Dylan Cecil was on holiday with his family when he slipped from a jetty. His body was found washed up near the town's yacht club on Friday.
A "beautiful" child with an "impish smile" that could melt hearts is how four-year-old Dylan Cecil who died after slipping off a jetty, was described at a memorial service.
Reverend Graham Witts led the service for Dylan, who died after falling into the sea while on holiday in Burnham-on-Sea, Somerset, with his parents Darren and Rachel.
Over 400 people attended the service at St Andrews Church to remember Dylan, whose body was found by a passer-by four days after he went into the water on mudflats, less than half a mile away at sailing club closeby.
A minute's silence has been held at Burnham-on-Sea in memory of Dylan Cecil. The four year-old fell into the sea from the town's slipway a week ago. His mother Rachel McCollum and Darren Cecil joined crowds for a minute's silent reflection in his memory.
The event took place as part of the town's rescue services day. It will be followed by a memorial service at St Andrew's Church.
Ms McCollum's father and Caroline Hall who lost her daughter Lelaina when she became trapped in low-tide mud near Burnham-On-Sea in 2002, spoke to ITV News. For more on this story visit the ITV News West website.
A one-minute silence has been held in memory of a four-year-old boy who died after falling into the sea from a jetty while on holiday with his parents in Somerset.
Dylan Cecil, from Kettering, wanted to get a closer look at the sea but slipped off the jetty and into the water at Burnham-on-Sea, a week ago.
Today, members of the community joined the youngster's parents, Rachel McCollum and Darren Cecil, and his two younger sisters, aged one and three, on the jetty for a one-minute silence in memory of Dylan.
A service is to be held for the youngster and those involved in the rescue effort at St Andrews Church in the town later today at 6pm.
Bears, flowers and football shirts have been left by well-wishers following the death last Sunday.
The family had been visiting grandparents in the town when the tragedy occurred.
Dylan's parents desperately tried to rescue him, but were unable to reach him and had to be pulled from the water by passers-by.
A rescue attempt was launched immediately involving Coastguard, lifeboats and police but the search was called off when they failed to recover his body.
A member of the public discovered his body on nearby mudflats four days later.
A memorial service is to be held for a four year old boy who died after slipping from a jetty into the sea.
Reverend Graham Witts, who will be leading the service, said prayers and tributes would be said for Dylan Cecil, who died after falling into the sea while on holiday with his parents in Burnham-on-Sea, Somerset last Sunday.
The boy's favourite Bruno Mars song will be played during the service at St Andrews Church in the town this evening.
Police have confirmed a body found yesterday off the Somerset coast is that of four-year-old Dylan Cecil, who slipped from a jetty into the sea.
Dylan was on holiday with his family when he disappeared under the muddy water at Burnham-on-Sea on Sunday. His body was found less than a mile away.
His family, from Kettering, Northamptonshire, said while they are still traumatised by what has happened they are grateful to have his body back so they can bury him properly.
The relatives of Dylan Cecil, who slipped into the sea from a jetty, say they are grateful after police believe they have found his body.Read the full story ›
Dylan Cecil's family have released this statement:
We would like to thank everyone for their help and support during this difficult time.
We would like to express our gratitude for all the messages of sympathy and support from both the local community and wider public across the nation.
In particular we would like to thank the people involved in the search – the police, RNLI, HM Coast Guard and the Burnham-on-Sea Area Rescue Boat (BARB).
We are still extremely traumatised but very grateful that it appears Dylan has been returned to allow us to bury our son.
Avon and Somerset Police have released this statement regarding the body discovered off the coast of Somerset:
The body is still to be formally identified but I believe it to be that of Dylan Cecil who went missing last Sunday evening.
An intensive search was launched on Sunday and continued throughout the night into Monday morning to try to find the missing boy from Kettering.
Well-rehearsed plans were rolled out involving the emergency services and agency partners including the police, fire, ambulance, HM Coast Guard, RNLI and Burnham-on-Sea Area Rescue Boat...
Dylan's parents have been made aware