The accepted answer of this question from last year covers your question I feel.
The quick of it is that the spell gives you the ability to move over water as if it was solid ground, but it’s not forced on you. You can choose not to use the ability and treat it as normal water for the purposes of crossing over it.
The bouyance part of that spell does say:
If you target a creature submerged in a liquid, the spell carries the target to the surface of the liquid at a rate of 60 feet per round.
So this presents two scenarios:
- Water Walk cast on you outside of water, you do not get the buoyancy benefit/detriment for the duration of the spell.
- Water Walk cast on you while submerged, you do get the buoyancy benefit/detriment for the duration of the spell.