Once the team descends, they'll find the sides the cenote to be layers of rock. Along those ledges are many hollowed and washed away areas. Most of these are mere shallow scoops in the rock, or caves too narrow for progress.

However, one grotto raised several feet over the water holds promise; aside from being more spacious, there's a whistle of air from a gap in the wall. It's large enough for a Moogle to fly through, but too small for an adult human. Still, the air flow felt on your side is promising, and the edges of the rock don't appear to be thick. (Your Moogles can confirm there’s a wider cavern ahead.) A powerful physical attack, explosive skill, or earth-based ability should be enough to chip away the excess stone and break it wide enough to enter.