There are quite a few devices that have made sea exploration as you know it possible. Submarines are one of these devices.
The compass and the astrolabe made navigation by sea, and therefore exploration, possible.
http://wiki.answers.com/Q/What_technological_improvements_made_exploation_by_sea_possible_in_the_1400"
The compass and the astrolabe.
Columbus
The two sailing inventions that made the Age of Exploration possible were Caravel, and the Galleon.
Techonlogical inventions which made the Age of Exploration possible included a sextant, which sailors used to navigate by the stars, and a compass.
The Caravel
the astrolabe and the compass
There are quite a few devices that have made sea exploration as you know it possible. Submarines are one of these devices.
the coronol, a spyglass for navigating
Bathyscapes and submersibles have.
the coronol, a spyglass for navigating