It could be 3 miles, could be 4 miles or could be 3 + 4 miles, but probably not 3 x 4 miles. The name of the house will be a big help in telling you just how far it is and what is nearby (walking distance).
For reference though, Blue Reef is 8 miles north, and now that Coastal Express offers regularly scheduled service to/from Blue Reef, you are in good shape so long as the house is 8 miles or less north of town (as far as having good, regular boat access). Sueno del Mar is 12 miles north of town and it's a 25-30 minute boat ride. The point being, that the difference in boat ride between 3 miles north and 5 miles north is very negligible.