Odd result when microwaving.

Factual Questions
1

This just popped back in my head after many years.
I used to work in a restaurant. I often had to microwave frozen peas.
I would empty the bag of peas into a plastic pail partially filled with water. The peas would be floating separately in the water.

After microwaving for a period of time that was not long enough to fully finish thawing them. Most of the peas would have clumped into a ball of ice surrounded by liquid water. Seemed an odd result. Start with separate frozen peas in liquid water. Add energy and get frozen peas in a clump of frozen water. As if the cold had been concentrated to the center area. Which doesn’t seem to make sense.

Any explanations?

2

But the same result if you just put the peas into the water and left it.
The microwaves just warmed the top of the water up a bit.

The water at the bottom was cooled by the peas.