Moana is a Disney film about a Polynesian chieftain's daughter, who heeds the call of the ocean and sets off to find a demigod and lift a curse. The film itself is rated PG for mild threat. This trailer was submitted with a U request and other trailers are already rated U. Watch the trailer, make a note of the issues and suggest a category, before comparing your decision and reasoning to that of a BBFC Compliance Officer - the person who watches the film and decides on the rating.
Remember that trailers do not always receive the same rating as the features they are advertising. This is because the viewing experience of trailers is different – trailers come unbidden to audiences who may have elected to see a very different kind of film. Often Disney's animated films are based on well-known fairy tales and this is based on traditional Polynesian stories. Does this look like a 'Disney Princess' film? Is it similar to any other films you may have seen?