500-200 BC Greeks developed trade routes in the Mediterranean using the length of the day (corrected for the time of the year) to estimate latitude.
450 BC Herodotus publishes a map of the Mediterranean region.
325 BC Pytheas, a Greek astronomer and geographer, sailed north out of the Mediterranean, reaching England and possibly even Iceland and Norway. He also developed the use of sightings on the North Star to determine latitude.
1698-1700 Edmund Halley made probably the first primarily scientific voyage to study the variation of the magnetic compass, sailing as far as 52 deg S. in the Atlantic Ocean. On a previous expedition to St. Helena, he made an important contribution to knowledge of the trade winds.
1768-1780 James Cook explores the southern parts of the oceans looking for the southern continent. He was the first to use a marine chronometer to determine longitude.
The renaissance of ocean exploration occurred in the 20th century, when human-powered exploration became increasingly popular. Via this new medium, pioneering has once again become the goal of ocean explorers.
Deep-sea exploration – Investigation of physical, chemical, and biological conditions on the sea bed
Exploration – Act of traveling and searching for resources or for information about the land or space itself