A slow boat to China will still get you there a LOT faster than walking.
Why is shipping so slow?
I figured I'd give building a navy a try. When I built my first ship I was amazed at how slowly it moved. Unless you are on an island, why would you even bother?
Shouldn't ships travel faster than your basic foot soldier? A good bit faster even than foot travel on roads? Shipping travels 24/7 but foot/mounted travel requires stopping to eat, sleep and maintain your mounts.