The four-year-old boy slipped as he ran towards the water with his mum and dad and two younger sisters, Faith, three, Alice, one, while enjoying a seaside break with their nan and grandad.
His parents jumped in to try and save him, but he was pulled under by a current that was said to be running at five knots.
His heartbroken mum, Rachel McCollum, 27, wrote on Facebook that she was 'destroyed beyond words - my heart, soul and life ripped apart'.
She and Dylan's dad, Darren Cecil, 31, were treated for the effects of swallowing seawater after their frantic efforts to find the little boy. They then spent 18 hours on the promenade at Burnham-on-Sea, Somerset, in the hope that rescuers would pull him from the water.
The sobbing mum was heard telling her partner that she wanted to give Dylan 'a cuddle and hold him'.
The little boy's nan and granddad, Dave and Jackie McCollum, laid flowers at the scene yesterday and said they were all 'devastated'.
"It is a terrible feeling knowing that my grandson is out there somewhere, all alone," Dave said. "He is a brilliant boy. He came to us with his sisters and his mum and dad. They were meant to be going home today, leaving the children with us. It wasn't to be."
"Dylan used to call us 'seaside nan and grandad' because we live here by the sea. His mum and dad are really cut up, absolutely devastated. We just want our baby home."
Dylan's nan Jackie, 47, added: "It is just unbelievable. We are all struggling to come to terms with what has happened."
The search for Dylan was called off at 4.30pm yesterday.