I'd also like to point out the way the melon exploded. As we see in the video, the top half of the melon basically explodes. This actually adds credence to the idea that the water-like substance inside the melon was rapidly heated to the point of boiling, because melons do not burst like that. A human crushing a melon between their thighs will cause the entire shell of the fruit to split and crack, usually more prominently on the top half (simply due to ideal placement concentrating the forces involved to that half). The melon can be further damaged by continued crushing, but it doesn't matter, because at this point it can pretty much be pulled apart by hand. The only feasible way for the top half of the melon to explode in the manner that it does would be for the material inside to become hot gas, and look for a place to escape. Because of the pressure being placed on the bottom half, I think that would mean the top half would provide less resistance to the steam, thus expldoing as violently as depicted.
I'd also like to point out the way the melon exploded. As we see in the video, the top half of the melon basically explodes. This actually adds credence to the idea that the water-like substance inside the melon was rapidly heated to the point of boiling, because melons do not burst like that. A human crushing a melon between their thighs will cause the entire shell of the fruit to split and crack, usually more prominently on the top half (simply due to ideal placement concentrating the forces involved to that half). The melon can be further damaged by continued crushing, but it doesn't matter, because at this point it can pretty much be pulled apart by hand. The only feasible way for the top half of the melon to explode in the manner that it does would be for the material inside to become hot gas, and look for a place to escape. Because of the pressure being placed on the bottom half, I think that would mean the top half would provide less resistance to the steam, thus expldoing as violently as depicted.