It's not really feasible as the canals existed a LONG time ago, namely during the time of Dutch settlement in New Amsterdam.

The ditch are expert canal builders and brought a lot of what they learned from developing their cities to the island of Manhattan.

However, while the Dutch were great canal builders, the English were great land builders. As in London, English settlers and their subsequent anglo-Nee Yorker descendants filled in acres and acres of the river and wetlands systems such that the edge the water where canals used to start are far from the rivers.

That being said Canals don't really make sense for New York. 200 years of development and infilling mean every square inch if Manhattan is densely developed high density urban landscape. It wouldn't be feasible nor beneficial to rip a canal into the city. No canal transportation could possibly compete with the high efficiency of rail in that kind of setting.