Still the distance up the coast is over 36 nautical miles from Ft. Lauderdale to the Lake Worth inlet. That's 7-9 hours for a tow off the coast, depending on whether they really were going more than 4 knots ;^).
Why a Bahamian couple with a Bahamian boat would come accross the Stream if their engine failed near Bimini is a question itself. Intrepid sailors, I guess...or something else?