It is fraught with tidal currents of strange twists and turns that are created by those two big islands on either side of it and by sand banks that extend out for many miles from both coasts. Most cruising boaters entering the Caribbean from the north do so via a stop at Samana in the northeastern part of the Dominican Republic, then continuing more than 150 miles across the Mona Passage to Puerto Rico without stopping. Add this to the twisted currents and seas encountered while crossing and a haze in the air in this region which often blocks visibility until only a few miles from land, and you come up with a never ending array of hair raising stories from just about every boater you can talk with who has made the crossing. Mona Island lies almost exactly in the middle of the Mona Passage and it would make an ideal resting place to split up the passage for vessels coming from Samana if it were only farther to the north. But for boaters wishing to take advantage of the island to break up the crossing into two more manageable pieces, they need to depart from the south coast of Hispaniola rather than the north.
Currents are also less treacherous to deal with along the southern route.
At the pleasant stop of Saona Island on the southeast coast of the Dominican Republic, boaters can sit and wait for a lull in the trade winds when seas are down to start their eastward crossing. This is an advantage which is not possible when departing from Samana. It is only about 40 miles from Isla Saona to the protected anchorage inside the barrier coral reef on the west coast of Mona Island. And from there it is another 40 miles to the popular and spacious cruising anchorage at Boqueron in Puerto Rico. Mona Island is a part of the commonwealth of Puerto Rico.