The mermaid nudity is not presented in a fanservice-y way and is not at all graphic. The "nipples" are basically just pink circles that are drawn on the breasts. It isn't pervasive either, and is only noticeable for a couple seconds at a time. What is more, depending on one's perspective, the non-human and fish-like nature of the mermaids can make the nudity come across as animal nudity.

Mermaid-like creatures appear with ocassional frontal nudity, but none of these instances are sexually related. (In the edited version, their nipples are erased.) In the first episode there is a brief (3 sec) shot of some adult magazines in the protagonist's room. (This is cut from the edited version.)

The series is based around a last stand for humanity against a psychopath scientist and his mutant army. Throughout the series the protagonists are fighting against robots, subs, and ships all of which are mutant creatures. When subs, which are giant whales, are destroyed there is large spurts of blood.

In one scene, a whale who helped the protagonist is torpedoed and slowly bleeds out. The water is stained red around the whale and the protagonist jumps into this water and swims to reach safety. Another scene shows a hand from one of the merfolk hitting the cockpit of a ship.

Violence toward humans is continuous with many explosions and destruction. Submarines and boats are seen exploding and breached sub show the crew areas flooding with people inside. A human facility is shown to be completely destroyed and any individual inside is inferred to be dead.

A final fight scene between a wounded shark creature and the protagonists shows a last violent showdown and is considerably bloodier than the rest of the series. The protagonist is hit hard and punched causing his face to bleed. The shark creature bleeds throughout from wounds in his arm and face.

The edited version significantly tones down the violence; some more violent scenes are cut altogether, while in other scenes the blood has either been digitally removed or recolored.

S and D words mainly. Cursing is infrequent, but occurs usually during intense situations. The edited version removes any actual profanity, but does leave in/add some crude slang like "choke on this".

The main character smokes throughout. Several scenes show him throwing away old cigarettes to light another immediately after. (The smoking is removed entirely from the edited version.) A character steps on a broken syringe which could have been used for drugs. No alcohol use is seen.

Intense action scenes throughout.

Lots of war violence and peril for the main characters. A shark creature can be frightening as he is very abusive to those around him.

A final battle is very intense and involves a lot of violence.

An edited version is available on DVD under the title "Blue Submarine No. 6: The Movie".