Sorry, but something is missing with this story, like deceased's drug use?

Unless pool was heated, and required a rapid chill for the swimmers, it would A LOT of dry ice to chill (1000lbs+ if a decent size 10,000+gal pool), furthermore, unless a pool is in hot sun for hours, normal ambient temps ( anything much below 98.6F) are a cooling effect on the body, you don't need dry ice, when regular ice would do.

Every concert in the 70's and early 80's had hundreds of pounds of dry ice visual stage effects, and NOBODY died.

Was it a breathing hazard, likely yes, but statistics are hard to argue with.

I say hoax.