We enjoyed our honeymoon in Fiji way back in 1991 and toured the islands with Blue Lagoon Cruises:
https://www.bluelagooncruises.com/fiji-princess/
The ship has room for only around 70 people and is small enough to be able to get into close range of many of the islands that make up the Fijian atoll. Had a FANTASTIC time with international guests from all over the world. The all Fijian crew was also a ton of fun! Mind you this was back in 1991...things may have changed.....but worth checking out!
Bula! (Hello in fijian!)
Alex