There is no access to a cave in the beta, when I play in a world with the "Caves and Cliffs" option activated, I cannot find an entrance to a cave or some kind of hole that gives us access to a cave, in the version of java if you can find holes that give access to a cave, but in the beta of bedrock there are not, if I enter a world with the option "Caves and Cliffs" disabled, if you can find holes and caves.
But if I activate the option of "caves and cliffs" the only thing I find are aquifers, in order to find a cave I have to dig until I find a normal cave or a mega cave.