I can understand why the US and Aussies are, but what is it with the Dutch? It seems they spend a lot of energy keeping the water out of their country. How did swimming become such a big sport in a country that doesn’t seem (to me) to be a natural home to it.
Probably for the reason you mentioned - for so long, they had to deal with flooding, and the people who couldn’t swim were weeded out by natural selection.
‘Welcome to Amsterdam, the “City of Cats and Canals” – which is a dangerous combination…’ (Remembered from Mr. Mike’s Mondo Video (1979), ‘Cat Swimming School’ segment.)
I don’t see how it makes more sense that aussies are good at swimming and not the Dutch - I mean, there’s only three or four million more of them than of us. As to the water thing, the Netherlands is the most natural home to swimming that you can think of. There’s water everywhere - we don’t try and get rid of it, we try to regulate it. We do this by building dykes and digging canals and ditches and what have you. Still, lots of water, look it up on google maps if you have to. As a result, every Dutch kid is required to learn how to swim when they’re four or five years old. So, while some slip through the cracks and never get their diploma’s, pretty much everyone in the Netherlands can swim. That gives a large pool - pun intended - to select olympic champions from. The large number of canals and ditches, which basically don’t stream and therefore freeze up easily, is probably also the explanation that The Netherlands has dominated speed skating for decades - even though the last time it was actually cold enough to do some actual skating on natural ice was over ten years ago…
What Švejk said. Swimming practice is compulsory at Dutch elementary schools.
Besides, the Dutch are tall, and that also helps with swimming.
Yes of course, they can allus put one foot on the bottom and tippy-toe along 
I would expect no less from a nation that evolved underwater. They had gills until relatively recently.
Probably because they’ve been driven into the North Sea by invaders so many times in their history. 
Your supporting post is fascinating–I can’t say I’d ever given much thought to the effect of height on swimming.
my first quick thought seeing the op question was: the canals thaw in the warmer months. and height is a big help.
skate in the winter, swim in the summer. world domination thoughts … perhaps during the spring and fall.
If you have been close to those canals you would know what an incentive the water is to getting out fast. That sure improves speed.
They thaw in the summer - I wish. The last time they thawed was in February 1996 - and they’ve been open ever since. And even then, the cities are always warmer and as a result, even in that year I don’t think it was safe to skate on the city canals (grachten) that the Netherlands is well known for.
good thing world domination is still in play!
The correct answer is “they are tall”. The canals are largely irrelevant as it’s not like they swim them for transportation.
The alternative answer is that they swim a lot.
The Chinese play a lot of ping pong. They win a lot of medals. 10 years ago, the British government invested $10 million in developing a cycling program. The Brits are now winning a lot of cycling medals. Bobsled is not wildly popular in Jamaica, and the trophy cupboard is a little bare.