Even if none of the fish wear clothes, this is very common in nature and in the sea, so it doesn't count as real nudity.

A few moments of relationships.

They play games with dragons

There is no blood, but some of the "violence" may look brutal.

"God," and "damn" respectively. Interestingly, the use of the song "Good as Hell" by Lizzo in the Season 6 episode "The Ultra Spy Tool" has it skip over the vulgar lyrics of it, despite "damn" being a stronger expletive than the latter one.

There is alcohol in some episodes.

They are only few small things. Like Gil saying "Aaaaaaaaah!". And in outside time, there are frightening characters in the stories.

Since the show is preescholer themed, it won't contain any true elements of frightening, but many, and i mean many episodes from later seasons contain some intense adventures, but kids will not even feel frightened and will enjoy them.

Many episodes deal with heartwarming moments like bullying, saddnes, etc. Some kids or adults may be heartwarmed at the situations and how the kids save the situation.

Some intense battles are in the show.

Some characters may get chased in some episodes.