"I was naked with a beautiful girl all day," the star of The Vampire Diaries, who turned 32 on Dec. 8, tells PEOPLE. "I had a shower scene that led into another scene were I was kind of half-naked and wet."
Though Somerhalder does confirm he was on the set of his hit CW show, he wouldn't say whether his character, the scumbag vampire Damon, finally scored with Elena, who is played by Nina Dobrev and definitely qualifies as a beautiful girl.
"Damon has a long way to go," he says of conquering Elena. "He tried to kill her brother."
So who was in the shower with the birthday guy? "It wasn't Stefan," he says of costar Paul Wesley's character. "I promise."
Though performing a steamy shower scene may be enough of a birthday present for most guys, Somerhalder is asking for more. On his big day, he also launched the IS Foundation, a non-profit that will "focus on biodiversity, reforestation, sustainable farming and green industries," the actor says.
For more information about the organization – and to help make Somerhalder's birthday wish come true! – fans can visit its Web site at isfoundation.com.