While there were many bodies of water explored in 1610, the most significant exploration in that year was Hudson Bay by Henry Hudson.

Here's why:

* Henry Hudson's Journey: Henry Hudson, an English explorer, set sail in 1610 in search of a Northwest Passage to Asia. He explored a large body of water that later became known as Hudson Bay. He spent the winter there, but his crew eventually mutinied and set him adrift.

* Significance: This exploration marked a major step in understanding the geography of North America and the Arctic. It established the existence of a vast, inland sea that was later crucial for fur trade and exploration.

While other explorations may have occurred in 1610, Hudson Bay's discovery was a watershed moment and remains the most well-known exploration of that year.