Great article! Adobe PDF required. http://www.history.navy.mil/nan/backissues/1990s/1997/ma97/blimp.pdf
That's a hell of a story! I can't believe the chap swam 6 miles after that long in the water. That said, one wonders what the point in the blimps was if support couldn't reach them in time to deal with the U-Boot.
The biggest advantage was that blimps allowed the Naval Command to know the locations of the spotted u-boats. From this information, the convoys and individual ships could be re-routed around the u-boat's location. The key element of submarine attacks, surprise, was negated. The spotted u-boat would then have to burn critical fuel, especially on the eastern seaboard of the US, to move into another area to find targets. It should be noted that the blimp crews fully expected that their patrols would result in their own death. Their devotion to duty has been long ignored.
An addition to the above post......... AIRSHIPS IN ANTI-SUBMARINE OPERATIONS IN THE ATLANTIC On 7th December, 1941, there were in the United States Navy five non-rigid airships of the K-type currently in use in the Fleet. This type of airship was being produced at a slow rate and, as late as July, 1942, there were only nine of these ships in existence. Since then the production rate has been increased and on 1st October, 1943, there were 53 K-type airships in service in the Atlantic. This number will be increased until there are a total of 90, the authorised operating complement of Fleet Airships Atlantic. During the early part of 1942 all airships were based at Lakehurst and operated principally between Montauk Point and the Delaware Capes. As additional airships became available, operations were extended until now airships are operating from Maine to Brazil, with Fleet Airship Wings assigned to the Eastern, Gulf, and Caribbean Sea Frontiers and to the Fourth Fleet. Up until the present time, the great majority of operations have been from mooring masts, and with no hangars available within hundreds and sometimes thousands of miles. It has proved practicable to base an airship at a mast for an average of 1,000 flying hours' operation without return to a hangar for maintenance. The airships have been flown and moored under conditions not believed practicable until war conditions made them necessary. The airship has demonstrated its stamina by averaging well over 250 operational flying hours per month per airship. The anti-submarine missions normally assigned to airships are : patrols of areas or routes up to distances of 200 miles offshore, aerial coverage of convoys within its operating areas and participation in bunts and searches. The missions are about equally divided between day and night, the airships being peculiarly adapted for night and low visibility work by their inherent characteristics. The airship does not normally engage a submarine against heavy A.A. fire but keeps the submarine under observation and summons support—always being alert to take advantage of favourable attack opportunities. At night and under low visibility, the airship has a fair chance of surprising the submarine and pressing home a bomb attack. The airships have performed considerable utility work in locating and assisting ship and plane wreck survivors (an unfortunate but necessary work in anti-submarine operations). The airships are also used in some areas to herd convoys forming up and to pass messages by line or voice to vessels at sea. The airships have performed the unspectacular but essential missions which fall to their lot in a commendable manner. Source - The United States Fleet Anti-Submarine Bulletin. (Date unknown)