Due to this lesson's topic, this will be a very short tip.
The sixth sea is a small sea, a very small sea. It is where all the water from the prior sea is squeezed and channeled to literally squirt the reader to the finale of the story. In a novel, this will range from the last couple of chapters to possibly the last few pages. In a short story, the climax usually occurs in the last one or two paragraphs.
This is Freytag's Pyramid Complex
As you can see, there are small buildups and mini-climaxes as you work your way to the major climax of the story. There is even the possibility of the sub-climax after the major climax, but it isn't a necessity.
In "Sea of Regret" our lead, Hanson, after making friends with Ayala, the mermaid, goes below the surface of the ocean, into another realm, her world. He cannot breathe, his lungs are burning. Deeper and deeper. Until he sees the other merpeople.
His lungs burned and he regretted not taking a deeper breath. Would he survive to surface again?
In the distance he could see others swimming toward them. Merpeople. The sea was full of them. They were coming to greet him. Hanson's exuberance suddenly faded.
It is at this moment that Hanson realizes what is happening.
Ayala turned to look at him and through the haze he could see that her eyes were dark, very dark. They were no longer anything like Shara Ki's. In fact, Ayala's soft smile now twisted into a grin, an evil grin. The sharp teeth glistened from behind the curling snarl of her lips.
It is at this point you have reached the pinnacle of your story, the climax!
Seaman Second Class Hanson regretted at that moment not listening that to what Ayala had said. They ate whatever they caught.