He commemorated their trip with an Instagram post on Tuesday, showing two Polaroid-like photos: one of the beach and blue ocean, the other of her curled against his chest.
He captioned it simply, “2-14-17.”
Duff’s romance with Koma is blossoming against the backdrop of new allegations against her ex-husband, Mike Comrie, with whom she shares a young son. PEOPLE confirmed earlier this week that Comrie is being investigated by Los Angeles police for alleged sexual battery.
While authorities could not provide further details, sexual battery involves a person touching “an intimate part of another person” without their consent, according to California law.
Comrie was later spotted out in L.A. and alone at his condo as news of the criminal investigation spread. (Calls to his representatives have not been returned.)
Duff and the former hockey player officially divorced in 2016 after separating in 2014.Before her relationship with Koma, Duff’s most serious boyfriend since Comrie was trainer Jason Walsh, as she revealed to Cosmopolitan this month. They split in the fall.