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If you look at OCEARCH's track for Katharine this year, you'll see she was off the Keys on July 17 headed north. Betsy doesn't have a good track, but presumably as she was in the Gulf of Mexico as recently as June 5 she may well have also been off the Keys in July (her next detection was just off Nantucket just a few days ago). So that's two we know of that were in the area in that timeframe this year. Last year there were a number of other sightings in the Keys during the summer.
They probably are out there; however from the tracked sharks it looks like they're spending more of their time offshore. That would limit the observations by divers and sportfishers. And not all the tagged white sharks have been down this way. Mary Lee's spent the past year nosing around Georgia and the Carolinas, Genie never made it farther south than the Jacksonville area, and Lydia was off doing Cousteau-knows-what in the middle of the North Atlantic for a few months. Sometimes I think they're just out to confuse us