I would have thought that childhood in 17th and 18th century North America would have included the occasional dip in ponds and rivers and that swimming would have been more commonplace even back then.
There is always more to say, but this broad topic has come up here a couple of times before, and you might like to review those earlier threads – which at least discuss the extent to which people from an American/European background swam in this period, and the cultural reasons why they did not – while waiting for fresh responses to your question
:What kind of swimming techniques would people in the 17th and 18th century use?, with u/sunagainstgold
Is it true that a lot of old-timey sailors couldn't swim? with me, u/mikedash
Sailors ability to swim in the 15th century with u/eternalkerri and u/Vampire_Seraphin