You will see through the ground. Diamonds, emeralds, iron, gold, and ancient debris (if on a 1.16+ modded server) will glow in the darkness as floating entities.
(This isn't X-Ray but helps see in caves.) xray hacks for eaglercraft
: Place a Composter , jump inside, and have a friend (or a piston) drop a gravity block like Sand or Gravel on your head. This will often allow you to see through the ground without suffocating. You will see through the ground