Which development most aided explorers in their ability to sail the oceans to discover the new world during the age of discovery

I believe it is the compass.  It aided sailors locate the direction to which they needed to go.  Even before the age of exploration, people had ships capable of long voyages.  As the years pass, the designed improved to an extent that they can travel farther.  

The development that most aided explorers in their ability to sail the oceans to discover the new world during the age of discovery is more efficient ships. During this time, explorers needed many instruments or tools in order to travel across seas. Ships were the most helpful for them because they were able to go from one island to another isalnd with ease. Some of the ships were the Caravel, Galleon and the Dutch ships. More efficient ships allow them to travel in larger distance while employng less resources.