James Christopher Tidd Chapman, 42, of Hazel Drive, in Ipswich, took 50 photographs during last year's Birdman in August - a number of which were close-up images of the underwear area of children as young as five.
Amanda Allemand, prosecuting at Worthing Magistrates' Court, said a number of families became suspicious when they saw Chapman taking photographs of children on the beach.
They called police, who then arrested Chapman after he refused to hand over his camera.
Miss Allemand said: "The camera and memory cards were seized and a number of photographs were discovered, many of young children on the beach.
"There were 50 images, the majority were of children about 10 to 13 years old, but in all, the ages ranged from two years old to 20. There were about four or five images of each person."
The court was told one of the images was of a child, about 11-years-old, who was wearing a red skirt. The image was a close-up shot showing the girl's underwear.
Miss Allemand said another shot was a close-up of a five-year-old girl sitting "half-naked" on the beach.
She added: "The officer who arrested the defendant said he was shocked and appalled at the images."
The prosecution said they would be applying for a sexual offences prevention order against Chapman.
Miss Allemand added: "The defendant admitted some of the images were taken for sexual gratification. He said photography was his hobby and he took photographs for artistic purposes.
Gareth Morgan, defending, said Chapman, a software engineer, had no previous offences.
He said: "The photographs do not amount to indecent images, the majority are children playing on the beach."
However, Mr Morgan said they did accept some were of the underwear area.
Magistrates adjourned the case for a pre-sentence report to be prepared.
Chapman was released on unconditional bail and will appear at Worthing Magistrates' Court again on May 4.
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