Police have issued a photograph taken of a two-year-old boy on the day he was found unresponsive in a lake in a bid to trace his final movements.
Greyson Birch was found in the water at Swanwick Lakes Nature Reserve in Hampshire on the evening of May 30.
He was taken to Southampton General Hospital where he died on June 3.
An 18-year-old man from Southampton has been arrested on suspicion of neglect and is on bail until August 30.
Hampshire police are now attempting to find witnesses who saw Greyson earlier on Sunday May 30 at Lakeside Country Park in Eastleigh between 6.45pm and 7.15pm.
A force spokesman said: “We are issuing a photo of Greyson taken that day so you can see the clothing he was wearing – a blue striped top, dark shorts, and white trainers.
“He may have had a small push-along bike with him at Lakeside.”
Detective Inspector Matt Gillooly said: “Our investigation is tracing all of the steps leading up to Greyson’s tragic death, and we are looking at places he may have visited prior to Swanwick Lakes.”
Greyson has been described by his family as a “character that neither family, friends or other persons will not and cannot forget”.
A tribute, issued through police, added: “His bubbly personality that filled all our hearts with joy and happiness will linger in this world.
“Greyson was our light and life that will still shine to us all through our thoughts and memories. Greyson would love to dance, sing, play, just everything.
“To know that each time we hear Twinkle Twinkle or someone plays Baby Shark and he’s not there dancing and clapping his hands kills us to the bottom of our hearts.”