A former teacher at a Devon boarding school accused of sexually abusing six pupils said he was "shocked, horrified and stunned" by the allegations.
Paul Couch, 61, of Wyndham Street West, Plymouth, denied two counts of sexual assault and 15 of indecent assault when he appeared at Exeter Crown Court.
The offences allegedly took place between 1972 and 1993 at the school, which is now closed, the court heard.
The prosecution has claimed some of the abuse happened during sailing trips.
Mr Couch told the jury that when sailing he would lift or steady boys as they transferred from the rowing tender to the yacht, but there was no indecent contact.
He said boys sometimes sat on his lap as they and others watched TV, but there was no sexual motivation.
Mr Couch told police the allegations were "disgusting and untrue" and any physical contact was "horse-play".
The trial continues.