Two thoughts spring to mind, but I'm sure there are many other examples to be offered as well. First, Tenochtitlan, the capital of the Aztecs (or Mexicatl, depending how technical you want to get) was on an island. There were causeways connecting the city to the shore, but those causeways had extensive bridges and removable decking to allow for all sorts of water traffic to move unimpeded. Tenochtitlan itself was also criss-crossed by canals. Several conquistadors compared the city to Venice, so that's a pretty ringing endorsement for the importance of watercraft in the capital's transportation infrastructure.

The second example that came to mind was that Pizarro's first contact with the Inca Empire was actually made at sea far to the north of the border of Tahuantinsuyu, the Four Quarters of the Inca's world. Pizarro's ship intercepted an ocean-going balsa-wood raft heading north loaded with mullu shells and other trade goods. How prevalent international trade was is much debated, but no one can doubt it happened at some level. It was literally the thing that brought the wealth of the Inca to Pizarro's attention.

I could probably cite a bunch of sources, but for the sake of brevity there's one historian who did sterling work on both civilizations: William H. Presscott's History of the Conquest of Mexico and History of the Conquest of Peru are only dated for their lack of archaeological content. In terms of primary document research, he was exhaustive. Presscott himself was a pretty interesting guy, too: He lost much of his vision as a result of a school food fight, and so his research was especially painstaking: He literally needed to hold his nose just above every line of every page he ever read. Fortunately he had an eidatic memory, so if he read something once, he always retained it. He often could use his memory even without understanding what he was reading at the time: He was able to recite word for word lenghty mathematical proofs without knowing how to work out the problem or even what sort of problems the equations were meant to solve. Anyway, lucky for us he fell in love with post-Renaissance Spanish history, and so he read everything in the original Spanish he could find before translating it into English and condensing it into a series of books meant for a mass audience (keeping in mind the mass audience in his time was actually the upper class of New England, not the general public, but still, these are not dull and dense reads). Many, many other books have been written since, but I would wager every English-speaking Inca or Aztec historian has read Presscott at some point, even after all these years.