Create a default PhysicsBody.BuoyancyInput. The PhysicsBody.BuoyancyInput.mask defaults to PhysicsMask.All so every attached shape contributes unless explicitly filtered out. The surface defaults to a flat horizontal water surface at the world origin ( PhysicsBody.BuoyancyInput.surfacePosition = Vector2.zero, PhysicsBody.BuoyancyInput.surfaceNormal = Vector2.up ).

public BuoyancyInput()