We've all heard that humans "evolved" from "lower organisms"

my rule for IDing Swimming types is: if it wades, no way; if it floats, then totes

dual-typing is definitely a thing though, gulls awks pelicans and kingfishers are flying/swimming. Albatrosses are pure flying but tend to reap advantages nominally considered the mainstay of the dualtype through superior movepool (another mark against the bullshit disproportionate diversity in the Flying type roster). Waders are all pure-walking.

I feel like the perching/paddling/preying/parading/pernicketing podiametric addresses some of the issues with the more simplified three-type model; the five types are a little more specialised than the existing Swimming typing, but it's mitigated by the problematically huge Flying typing getting separated out into more manageable categories.

Just my 2c