Livro baseado em um mundo da água com um soberano monstruoso

Jack Vance's O Mundo Azul tem todos os elementos que você fala sobre.

De acordo com sciencefictionruminations :

In the distant past a spaceship crashed on the Blue World which consists of one gigantic ocean. The survivors discovered floating “pads” which are connected to stems which grow in clusters. [...] The primary purpose is to alert the other pads to the arrival of King Kragen and his lesser minions! King Kragen is a gigantic vindictive sea monster. The pads’ inhabitants have developed a policy of appeasing King Kragen who still occasionally wrecks havoc destroying buildings, eating sponges, and breaking nets.

Sklar Hast, our rebellious hero, is an apprentice hoodwink (communication tower operator). Sklar believes that the policy of appeasement should be replaced with a policy to exterminate King Kragen so the pads can finally live without fear. He invokes the ire of the more traditionalist members of the the society. After an audacious attempt at killing King Kragen, Sklar Hast is forced to leave the pads with his followers.

De acordo com o meu comentário, vou expor a possibilidade de este ser o da China Miéville. Scar , segundo livro do Bas Lag Cycle .

Aboard a vast seafaring vessel, a band of prisoners and slaves, their bodies remade into grotesque biological oddities, is being transported to the fledgling colony of New Crobuzon. But the journey is not theirs alone. They are joined by a handful of travelers, each with a reason for fleeing the city. Among them is Bellis Coldwine, a renowned linguist whose services as an interpreter grant her passage—and escape from horrific punishment. For she is linked to Isaac Dan der Grimnebulin, the brilliant renegade scientist who has unwittingly unleashed a nightmare upon New Crobuzon.

For Bellis, the plan is clear: live among the new frontiersmen of the colony until it is safe to return home. But when the ship is besieged by pirates on the Swollen Ocean, the senior officers are summarily executed. The surviving passengers are brought to Armada, a city constructed from the hulls of pirated ships, a floating, landless mass ruled by the bizarre duality called the Lovers. On Armada, everyone is given work, and even Remades live as equals to humans, Cactae, and Cray. Yet no one may ever leave.

Lonely and embittered in her captivity, Bellis knows that to show dissent is a death sentence. Instead, she must furtively seek information about Armada’s agenda. The answer lies in the dark, amorphous shapes that float undetected miles below the waters—terrifying entities with a singular, chilling mission...

Esse último bit refere-se ao Avanc , uma enorme criatura marinha. O livro também apresenta os Scabmettlers , uma raça cujo sangue coagula rapidamente, com o qual eles criam suas próprias armas. e armadura.

É um livro mais recente (2002), mas ainda é quatorze anos atrás. Não é um planeta aquoso, apenas uma seção que tem muita água (embora, francamente, a Terra também). A criatura marinha é levantada mais tarde no livro. Honestamente, não é o melhor jogo, mas está perto o suficiente para que eu ache que eu posaria isso.