Please Help me achieve this effect.

Hey guys,

For example you can’t swim across water so you’ll need to drop a box of ice on the water so that it turns into ice.
Now my question is, how can I achieve this effect? Is there like a dual layered shader with a fade or something?
We have a dissolve shader and it is possible to make a plane with texture 1 dissolve and beneath that one another plane with texture 2.
But It would be more work to do so.
Also it needs to be triggered by script.

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