*laughs again* You know, I had an odd thought about how technology would develop in a mermaid society. Perhaps they mine for air for various uses below the surface? :D

Air nothing, water is much more adept to transferring heat, not to mention it has a much higher thermal density. So the ice cream would not only melt faster from the increase thermal conduction it would also take more to cool the same area of water down. Now combine that with warmer ocean temperatures that are around 70-80 Fahrenheit and you have a recipe for disaster, or as least ice cream soup....which too would be ruined due to diffusion.

TL;DR
It's goina melt, she's going to be sad.

I hope she cries. The tears of tender young squids are my favorite food.

You are a mean and uncaring bitch D:

*blinks* What I sayeth has no relation to ice cream! I mean, as a legitimate trade of business, air mining :D I wonder if one could pump air to the ocean floor. Maybe they could make a rotating scooper that harnessed air as well. :P