A Nazi sub has been found off of the Texas coast.

How was a u-boat able to penetrate that closely to America (especially given that the positioning of Cuba between the Yucatan and Florida peninsulas provides two relatively narrow choke points) and stay supplied for a mission? Where and how would this boat have gotten replenishment fuel, food, and ammunition -- were Nazi sub tenders also coming this close, or did the boat have to make a trip back into the Atlantic to resupply?

And, how effective were they? How much shipping were they able to sink? Were they a persistent threat to American waters throughout the war? Were significant resources diverted from the main war effort to counter this new threat? What was the propaganda value of such excursions to the Germans?

Any additional info or follow up questions are encouraged, this is very intriguing to me. I knew U-boats had lurked off the American east coast, but that they had made it into the Gulf is surprising!