The maximum penalty for each charge is 10 years' imprisonment.
In a video of a police interview with her, one of the girls, aged 10 at the time, said she wanted to tell the man to go away but did not want to be rude.
The defendant faces four charges of indecently assaulting her. On each occasion it was alleged he touched her right upper thigh.
The girl said she was playing in the lazy river at Alpine Aqualand with friends on June 8, 2017, and "there was this guy going around touching my thigh''.
She alleged the man was "crouching'', so the water was close to his chin, and went around the lazy river about 10 times.
The first time he allegedly touched her she thought it was "an accident''.
"The first time he actually pushed it [her thigh], but all the rest of them he swiped it.''
Crown prosecutor Riki Donnelly told the jurors they needed to be satisfied there was a deliberate application of force, and the assaults were indecent.
"That force need not be forceful.
"It simply needs to be the deliberate application of force, even if it's only very slight touching.
"Some of them [the allegations] may not appear overtly indecent at first blush ... but indecency does not require touching to [erogenous] areas.''
Defence counsel Hugo Young told the jury many of the allegations of touching or physical contact "did not happen'' and in "many instances'' the complainants were mistaken about being touched.
The defence maintained it was "by no means certain'' the defendant was the person responsible for all of the touching, or contact, that did occur; any instances of physical contact between the defendant and any of the complainants was accidental; and there was "never any intention on the defendant's part to do anything indecent to the complainants.''
The trial before Judge Mark Callaghan continues.
