You decide to enter the cave. For one thing, it looks and feels like it might rain, and that's the only available shelter right now. However you also vaguely hope that it might bore out and up through the cliff, getting you off the desolate beach.
The insides of the cave are fairly smooth at first, a natural passage seemingly hollowed out by water. The soft white sand of the beach extends to the floor here, making it easy going, and there's a promising upward incline.
The walls get a bit rougher as you go in, and the light from the cave mouth fades. Before you can really worry about illumination, however, a new source of light appears ahead. Excited, thinking it another exit, you press forward. Although you haven't gone nearly high enough to have reached the top of the cliff, it's promising.
However, to your puzzlement, the cave dead-ends in a moderately large chamber. You blink at the sight of light reflecting off a shimmering pool of water, reflecting off of moisture-slick limestone stalagmites and stalactites partially fused to the wall beyond it, and glittering in mica and quartz crystals in the walls. But you don't see a source for the light, and realise with a bit of a lurch that it's coming from the water itself.
However your attention is quickly diverted by the glitter of something else. Gold! Your eyes widen as you take in several mouldering chests overflowing with coins, jewels, and trinkets. Drawn by curiosity as much as greed, you wander over towards the trove. It isn't exactly a king's ransom, but it's certainly more wealth than you've ever seen before.
Unfortunately... You grimace as you look between the treasure and the pool. Closer to the water's edge, you can see down into it, and the pool appears to be bottomless. But you don't think that's a way out -- even if it connects to something else, you've not exactly a world-class diver. And while the gold would make you rich, you'd need to get it out of here. Meanwhile, you can't eat it.
Still... There are some interesting items here. Necklaces, rings, even a slender circlet or two. A few weapons propped against the wall, leather scabbards and wooden hafts suspiciously free of age in contrast to the rotting chests. You run a hand through your hair, thinking maybe you could examine the treasure just to pass the time. Or maybe taste the water to establish if it's flesh, though the glow emanating from it gives you pause.