I wonder if it’s even possible to fill an Olympic-sized pool with ants without crushing the ones near the bottom.

A column of ants 2M high would be about 1000 ants (assuming 2mm height for an ant). According to [1], ants range from 1mg to 150mg(!) but most commonly 5-10mg - call it 8mg as an average and your bottom ant would be supporting about 8 grams over an area of (I assumed in another comment) 9x4mm or 36mm^2 to give about (if I'm operating [2] correctly) about 0.3psi. [3] suggests that ants can lift about 5000x their own weight which should mean the bottom ant would not only be fine but could probably carry the 2M column around without any trouble...

[1] https://whatthingsweigh.com/how-much-does-an-ant-weigh/ [2] https://www.sensorsone.com/force-and-area-to-pressure-calcul... [3] https://entomologytoday.org/2014/02/11/ants-can-lift-up-to-5...