Ice cubes floating ... or not

[Odin]

Yesterday I made a Pure Whiskey and threw in some Brita filtered water. I shaked the bottle a bit and poored myself a drink. I added an ice cube. To my surprise the cube settled at the bottom of the glass. The glass being a tulip shaped, narrow genever glass.

Today I took measurements. Turns out the drink was 68%.

I diluted it further to 50% and poored myself another drink, adding an ice cube in the process. This time the cube stayed on top.

Is it like this that water (frozen) has a lower density than 50% abv likker, but a higher density than 68% likker? And that's why it floats on one occasion and settles at the bottom of the drink in the other situation?

Odin.