Scaling trigger when particles enter

Hi Unity Community!
I want to scale a trigger up in Y when OnParticleTrigger (i.e.: a pool filling with water when water particles enter)
I've figured out how to do it OnParticleCollision, but the problem is, I need my player to be able to enter the pool and swim (this is why a trigger would be preferred). OnParticleCollision only works for non-trigger colliders

Code (CSharp):

1. void OnParticleCollision (GameObject other)
2.     {//This checks if our colliding object is a water container
3.         if (other.GetComponent<waterContainerScript> () != null) {
4. //This adds water to our container (scales up in Y)
5.             other.GetComponent<waterContainerScript> ().AddWater ();
6.         }
7. }
8.  

I checked out the OnParticleTrigger documentation, but it only talks about changing particles within a trigger, not modifying the trigger itself. Does anyone know how I could achieve this?