You eventually decide to take the tunnel labeled " mer-folk" out of interest on what a mer-folk could be some kind of fish species that has been extinct for thousands of years or just undiscovered you would be famous and rich!
While you think about what you would do with that massive amount of money and fame people would be like "oh my god its that young handsome rich guy who found that new species the mer-folk!" You think about how people would worship and bow to you or forever be shunned by you. While daydreaming you feel your shoes start to get wet and make a weird noise underfoot you step back in response and take in your surrounding.
You observe the cave and see a large cave with and murky lake taking in most of the space in the cave and candles line the walls.
You start to ponder the origins of the cave who could of built it an ancient unknown civilisation that know one knew about that know about an extinct fish species or a secret cult that worship some kind of god that made a fish species as a present for there worship or a mad scientist that created a horrific fish mutant that was to horrible for any human too see.
Your wild conspiracy theory thinking session is interrupted by ripples in the water and as you lean down towards the water too see bubbles rise from below the waters surface you lean towards the water when your pulled below the water and you black out