Because Bean Island is, well, and island, you may think at first that you need either a boat or an impressive swimming ability to get there; but the fact is, it's easier than most people would assume.
Using a small boat or raft like a kayak or a paddle board is probably the best option, but if you don't mind getting your legs wet, you can actually walk there!
The southern coast of the island is only about 96 feet (32 yards) from the mainland, and the thin strait separating the two is incredibly shallow, measuring only about 2.5 feet in depth at its deepest point. This means that you can walk directly across it with no issues! Just make sure you're wearing shorts. The strait is located off of Lakeview Ave, Natick, with access to the lake provided by forest trails that you can enter at the west end of the street.
FUN FACT: The strait separating Bean Island from the mainland off Lakeview Ave is named Fiddlum's Strait after local man and ice cream vendor Barney Fiddlum Sr., who became the first to cross the strait and subsequently the first to reach the island in 1897.
Below are a few informational maps showing the width of Fiddlum's Strait and the location of Bean Island in Natick.
The location of Bean Island is marked. (Interactive Map)