Animation Age Ghetto: A definite attempt to work around this. In the end it was killed more by the production costs (compared to the income it was getting) than by breaking the "for kids" rule.
As for the age perception, it was noted for really managing to work around this - it was still quite kid-friendly but was way more complicated than other shows of its time, with a Myth Arc.
Chickification: When Tula is introduced, she is a capable sailor Action Girl with her own agenda. After she finds out about her magical powers, she not only gets a more revealing outfit, but is mostly shown either swooning and moaning because of using said powers, or just shouting at other characters and needing some sort of rescue.
Complete Monster: The Dark Dweller is the being behind the titular "Dark Water," a menacing oily substance that devours whatever it touches and is spreading all throughout the world. By proxy, the Dweller is responsible for countless deaths of places that the Dark Water has devoured. The Dark Dweller is focused on domination and destruction who plans to unleash its Dark Water throughout the world, focused only on consuming and controlling what it can.
Forgot About His Powers : Tula finds out she has the power to influence nature, weather, plants, and animals... and promptly forgets that when the ship could use additional wind, or a toxic fog should be dispersed, or when she's in danger from animals...
"Funny Aneurysm" Moment: Niddler's obsession with food and his cowardice both become a lot less comical when you recall he's a member of a slave race who was sold to Bloth of all people. Starvation was clearly a big part of his life before Ren rescued him, and courage likely wasn't rewarded by either the slavers who raised him or the crew of the Maelstrom...
Ho Yay: Young and (as much as we can tell) pretty Tula runs about with a bare midriff among seamen (snicker) and the only one who really takes notice of her is Bloth, of all people. Ren seems pretty comatose when it comes to the opposite sex, and while Ioz does mention that he enjoys women, he keeps grabbing and hugging Ren by the waist. Also, Ioz and Zooley are pretty shippable.
Narm: In Andorus level in the Sega Genesis game, you have to work your way through networks of caves infested with savage beasts and pools of dark water, accompanied by an almost hypnotic while also creepy background tune. All of the quiet menace is a little undone by the farting noises made by blobs of dark water shooting out of pools, though.
Nightmare Fuel: It's never pretty when Dark Water gets a hold of anything or anyone. In one episode, one drop consumes someone from the inside out.
The Constrictus isn't particularly pretty either. And Bloth is bound to cause sleepless nights for anyone who stares at his face too long (i.e. any length of time).
The opening of episode four. Skulls and bones and creepy ship and carnivorous dragons...
Ren's eyes NEVER move, although that may be more Uncanny Valley. Especially since half the time he's looking directly at the screen when there's no way he should be able...
Adding to this, All three main heroes are blonde, Ren, Galtar and Sara. Each team contains at least one displaced royal, Ren, Goleeta and Zorn and Sara. The main villain is responsible for the deaths of parents. Bloth is responsible for Ren's father's death, Tormack killed not only Galtar's parents but Goleeta's too. Diabolyn is responsible for Sara's mother's death.
Take it one step further: Brock Peters (aka Joe Sisko) also voiced Galtar's main antagonist; a couple of years later he would also voice Dark Kat for the studio. Making that series Older Than They Think as well in terms of recycling.
Brock Peters did have such an epic voice, a great pick up for the studio to give roles to in the 80s/90s. Too bad he didn't do more.
Also this would be the second HB show to have its heroes on a quest for 13 of something. See The 13 Ghosts of Scooby-Doo. In process also making it the second show to not complete a quest for 13 of something either.
Seasonal Rot : After a great start, with changing loyalties, various factions, reveals, dramatic deaths and competent villains, there comes (from Andorus onwards) a sequence of filler episodes in which Ren becomes more naive and easy to fool, Ioz becomes dumb muscle, and Tula is [[Chickification chickified]] badly. Further treasures are found almost as an afterthought in otherwise Monster of the Week storylines.
Squick: In the episode "A Drop of Darkness," Cray is insistent on marrying Ren while calling him Primus. A whole new level is taken when considering that earlier in the episode Cray muses that Ren might have been her son.
And any of Bloth's crew. Scratch that - any bad guy. Konk can fit his entire hand up to the wrist in his giant maw. And does.
Villain Decay: In the miniseries, Konk is a very capable bad guy saddled with incompetent minions, capable of giving the heroes a difficult time on his own. He is later downgraded to being an incompetent minion himself.
They Wasted a Perfectly Good Plot : Ren learns that his father distributed the treasures he had found among his seven trusted companions. So when Ren and his friends are looking for them, they must have been hidden anew by these companions. However, there is no mention of this. It could have been a great addition to the story arc to see those seven, learn of their relationship to Primus, and the reasons why they chose such and such hiding places for the treasures.