Zac Efron and Michelle Rodriguez have a ''healthy influence on each other.''

The 'That Awkward Moment' star's close pal Gianluca Vacchi, who has been holidaying with the new couple in Sardinia, has defended their relationship amid speculation the actor's friends are concerned about him spending time with 'The Fast and the Furious' star, as they have both been in rehab in the past.

Gianluca wrote on Instagram: ''Don't be concerned, Z and Mich have a mutual healthy influence each other and they are very cute toghether (sic).''

Zac, 26, and Michelle, 36, were spotted kissing on a yacht last Sunday (06.07.14) and also couldn't keep their hands of each other in an Italian nightclub.

News of the couple's romance comes just weeks after it was revealed that the 'Bad Neighbours' star - who dated Vanessa Hudgens and Lily Collins in the past - was ready to start dating again.

A source previously said: ''Zac wants to date someone who's not intimidated by fame and who can challenge him intellectually.''

The hunky star appears to be getting his life back on track after checking into treatment facilities twice last year to allegedly seek help for substance abuse and alcoholism.

Michelle, who was most recently linked to British model Cara Delevingne, was sentenced to 30 days in rehab in 2006 after pleading guilty to Driving Under the Influence (DUI).