Why did europeans start sea exploration?

In part, Europeans began sea exploration in the hopes of expanding their empires and colonising new countries. They also began sea exploration to find new trading partners, new goods and even new trade routes. Some set out also to discover new areas of the world, especially as when sea exploration first began there were still sections of the world that still remained unknown in Europe - e.g. on maps in the 16th century many of the continents in the Southern Hemisphere were marked wrongly or did not exist