When you dismount any rideable entity (boats, minecarts, pigs, horses, striders) below y=0, when you're in water or lava, it will teleport you up to y=0, causing you to fall down, possibly to your death. This only happens when enabling Caves & Cliffs experimental toggle.
Step to Reproduce
1. Go find any big new cave below y=0.
2. Go find lava or water aquifers, make sure to have a big space up left to y=0, so you don't suffocate.
3. Try to ride a strider on lava, or row a boat on water.
Expected Results
You should be teleported down at the same level as you were riding.
Observed Results
You get teleported up to y=0, and you may fall down to your demise.
Can Confirm but for me it didn't teleport me to Y0 instead it kept teleporting me randomly in another location in the Lava Aquifer