The world's biggest cruise ship is a "construction site and a serious risk to all passengers" its first paying passengers have claimed.
Harmony of the Seas left Southampton for Rotterdam on a four-night cruise on 22 May, but customers complained about closed attractions and ongoing work.
Passenger Georgina Davie described "queues of complaining guests and distressed families".
Royal Caribbean Cruises admitted "final finishing touches" were being made.
Passenger Jonny Hardy tweeted the £783m ship was "not ready".
"Really not pleased work is still going on when they have over 6,000 passengers," another passenger Alex Parker also posted.
'Great value offering'
Ms Davie contacted the BBC and described the ship as "a construction site... unsafe and a serious risk to all passengers".
"Ninety percent of the kids attractions that it was marketed for have been shut for the whole cruise and are still being worked on."
She also claimed drilling went on near cabins through the night.
A spokesman confirmed the trip was not a "shakedown cruise", during which a ship's systems and facilities are tested.
"Whilst the majority of the ship's features are open and already being enjoyed by thousands of guests, as with any new build, we are still making some final finishing touches," he said.
"These early sailings were made possible due to the early delivery of the ship and we hope this has been reflected in the great value offering guests secured for their holiday."
The ship can carry 6,780 passengers. It has 20 restaurants, 23 swimming pools and took more than two-and-a-half years to construct.
It is due to leave the city again for a three-night cruise to Cherbourg later, before finally leaving Southampton for its summer base of Barcelona on 29 May.
Analysis - Paul Clifton, BBC South transport correspondent
It's quite normal for new cruise ships to have teething trouble and shipbuilding schedules are so tight, I've often seen workers laying carpets and hanging picture frames just hours before the first passengers get to their cabins.
But that should change when people get on board for their holidays. They have paid for luxurious facilities and high class entertainment.
That's why we have seen dozens of disgruntled travellers taking to Twitter - they feel let down.
Royal Caribbean has admitted getting things wrong on the world's largest cruise ship. But it has obviously not dented confidence - yesterday it ordered a fifth ship in this giant class - from the same French shipyard.