Answer:
Generally, cities built near water have two main advantages: commerce and sustainability.
Commerce: Cities near water allow for water transportation, which is generally faster than land transportation. This is especially true in older times (before the invention of trains, for instance). Cities with access to water trading routes could deliver great amounts of goods for trade with other coastal cities, which ment more money and trade goods for both settlements, and allowed for cultural mixing. Landlocked cities, on the other hand, were limited to land trade routes only, which tended to be slower and in some cases more costly.
Sustainability: Rivers, lakes and the sea provide food and other resources, which help the population of coastal cities to grow and expand faster than landlocked settlements. All cities require food, ant the more the better. While inland cities could only rely on agriculture, foraging and hunting, coastal cities ALSO had access to the flora and fauna that lived on the water bodies next to them. Plus, fresh, drinkable water is necessary for people to thrive, and building a city next to a fresh water source was a huge advantage over settlements built in other places, where they had to look for water sources, or build aqueducts to bring water to them, such as the city of Jerusalem. Moreover, water was also used as waste disposal, which allowed cities to remain "cleaner" that their inland counterparts, as the garbage and stools (sorry, I found no better word) of the people were washed away.