Would it sink down to a certain altitude based on how hollow the geode
is or would it float on top or sink to the bottom?
Most geodes are made of quartz or calcite. Their densities are somewhere between 2.6 and 2.7 g/cm3. Let's round it up to 3 for simplicity. This is three times the density of water.
So, for a geode to float it needs to be at least two thirds empty volume.
But! This is assuming what's inside is air. Geodes form from various fluids or gases. When they formed, if they had a fluid inside, and it is no longer inside, then the geode is not hermetically sealed. This means that once you drop it in the ocean, water will start leaking inside and it will eventually sink. If the geode formed from gas, and it is sealed, then yes there is a chance it will keep on floating.
And could geodes form in the ocean and then break loose and be
released into the ocean?
No, because if they form in the ocean, they have seawater inside. Not air. So their density cannot be lower than that of seawater, and they cannot float.