Is that the best example to use, though? Ideally to promote skepticism you want correlations which are the result of sifting through mountains of data for coincidences, or correlations where the only underlying causation is something grossly general like "things often change monotonically for decades as time advances". With "ice cream consumption versus drownings", I wouldn't be surprised if there's a real, specific common factor: high temperatures motiving people to eat more cold treats and go swimming more often.