The mermaid has you pinned against the wall and you struggle to break free. You have feel to push off from the wall with and that makes the difference. But the mermaid has a good grip on and doesn't let go. As you wrestle with the mermaid under water, you realize you're kinda being turned on by all this. You don't want to drown, but it's still wrestling with a beautiful mermaid. Maybe if she hadn't tried to trick you, things might've gone much better between the two of you?
You roll over and over it the water with the mermaid before colliding with the wall of the pool again. It doesn't hurt your back to bad. But the physics of momentum do their thing and a moment after you collide with the wall the mermaid's body collides with yours...and your waists are positioned such that the collide impales her up on your eretic "sword".