Zac Efron and Nina Dobrev Spotted Chatting Closely on Yacht

Zac Efron and Nina Dobrev were spotted looking pretty chummy with each other this week ... getting close as they chatted on a yacht during their sun-soaked getaway with friends in Sardinia.

Check out the pics ... the actors appeared comfortable with each other -- standing quite close -- as they let out a laugh while their vessel sailed into Porto Cervo at sunset.

It wasn't all fun and games ... earlier in the day, Nina looked somber as she was comforted by her friend Keleigh Sperry on the upper deck, Zac nowhere in sight.

It's not clear what may have upset her, but as you know, she and her longtime partner Shaun White just called off their engagement to the astonishment of fans.

As we reported, the "High School Musical" alum, Nina and Keleigh set sail together this week for Ripple Labs CEO Brad Garlinghouse's Italian wedding. Keleigh's hubby, actor Miles Teller, also joined, along with Chace Crawford and his model girlfriend Kelsey Merritt.

The group was spotted earlier this week splashing around and having a ball as they swam, jet skied, paddle boarded and more -- the men even jumped into the water from the top deck of the yacht.