they were afraid Zeus might blast them out of the sky
anywhere they wanted but they never came very far by land travel
Boats
The Ancient Greeks traveled by the sea because the land was to mountainous to travel by foot. The Ancient Greeks traveled by foot, cart, chariot and ship.
Basically because it was one of the earliest known way to travel.
Yes. However, the land that is now Greece is composed of a LOT of islands, so in ancient times they were as likely to sail as to walk.
On land, good roads made travel possible as never before. On sea, knowledge of the weather conditions and shipping lanes was a factor.
Take a look at ancient Greece on a map. There are many islands and much coastland. Travel by water is much faster than by land. The ancient Greeks traded with many people all around the Mediterranean.
Greeks travel by foot, cart, and ships.
They would travel on foot or by the use of horses when it came to land travel. Often times, especially soldiers who would have to travel country to country, they would eat opiate leaves during the journey to mask the pain in their feet from extensive travel. Boats were built for any sea travel.
By the water
In the days before air and motorised land transport, travel by foot, donkey, horse and oxcart was excruciatingly slow. Sea and river transport provided relatively good speed and volume.
Ships were invented prior to written records. Thus, we do not know who invented them. Ships were useful to the Greeks because they allowed travel to various islands and they permitted trade, which would have been far more arduous over land.