So, I am writing a comic which will perhaps grow into an entire series about a group of aquatic heroes. One of those heroes is a monster size aquatic lizard. The story of how this lizard came about is complicated and is addressed in the comic but for simplicity's sake here, it was a lab error. Scientists were breeding lizards to try to figure out some genetic mysteries and it lead to there being a clutch of about 10 eggs that would develop into monster sized aquatic lizards.
This accidentally hatched lizard hybrid is now out in the wild and is colloquially referred to as "The Komodo of the Sea". Now in this alternate universe, the existence of this monster lizard is not leading to species extinction.
Now, I will ask in future questions about the specific features of this monster lizard and its habitat and life cycle, but for now I will be asking about the size of it. I already mentioned that it is The Komodo of the Sea. This already gives a clue about the size. It is at least as big as a Komodo Dragon.
Now that is a giant lizard. It weighs about twice as much as an average human and is about twice as long as well. Prehistorically, there was a relative of this giant lizard known as Megalania. It was about twice as long as a Komodo dragon and more than 3 times heavier. So there is no doubt that a monster size lizard could exist. And, given that this monster of a lizard is aquatic, it wouldn't be surprising if it could grow bigger than Megalania. No bigger than a blue whale obviously because at that size, if it gets bigger, it will likely collapse and not be able to breathe.
Sure, hollow bones would ease that weight but they are fragile and not ideal for an aquatic animal. In fact, I do believe the water pressure would cause the bones to become more dense. And I know that bone density contributes a significant amount to weight when you are talking about giant animals.
Is it possible that this aquatic lizard could grow up to 50 feet long, as long as a humpback whale given the inverse cube law and that the lizard is aquatic? How massive would it get at that length?