Tom Holland spent months in a water tank playing a boy undergoing the most harrowing of circumstances — being swept up in the 2004 tsunami while vacationing in Thailand.

Now 16, the English thesp played the oldest of three brothers in “The Impossible” after a stint as Billy Elliot on stage in London.

“It wasn’t physically tiring since I had just come off of doing ‘Billy,’ but it was mentally challenging because I had to cry and go through all of these emotions that I had never experienced before in real life,” Holland says. “But because I was 13 when (we shot the movie) I really enjoyed that aspect of the filming process because it felt like I was in my very own water park.”

Holland wasn’t the only young thesp battling the elements on set: Suraj Sharma spent months preparing for the “Life of Pi” shoot, while Quvenzhane Wallis battled swampy bayou conditions during the “Beasts of the Southern Wild” shoot. They were among several notable performances by the underage set this season, including Jared Gilman and Kara Hayward (“Moonrise Kingdom”), Xzannjah Matsi (“Mr. Pip”) , Elle Fanning (“Ginger & Rosa”) and Saoirse Ronan, who hadn’t turned 18 when she filmed Neil Jordan’s “Byzantium.”

Sharma, a South Delhi native who had no prior acting experience before being cast as Pi in the film adaptation of Yann Martel’s Booker Prize-winning novel, turned 18 on set. To prepare for the arduous role, he practiced yoga and learned how to swim. With Lee’s help, Sharma learned how to maintain a persuasive rapport with a virtual tiger on a cramped boat on an outdoor wave tank in Taiwan.

“I think he was trying to build Pi little by little inside of me over the prep months, so that later, when we were shooting, (my) acting would be minimal — more natural,” Sharma says.

Now 9, Wallis was only 5 when she was cast as the indomitable Hushpuppy in “Beasts.” Despite portraying a motherless child who lives by herself in the face of great danger, the newbie says shooting was “fun.” The most difficult aspect? “Louisiana mosquitoes!”

Eye on the Oscars: Talent Race
What’s their damage? Plenty | Thesps weigh reel-life choice | Great performances in genre movies | Minors show their pluck in grownup fare | Seniors grab center stage | Roles all over the map in this ‘Atlas’ | Repeat contenders