Had a quick conversation with Agent Wright over in Miami about his investigation into the port. It's part of the routine inquiries these days, but he already knew there wouldn't be any leads. In fact, Jimmy had given up on the investigation before.
Winston undeniably has some highly professional personnel at his disposal. Not to mention that planting explosives on a yacht without anyone noticing is no small feat. The precision required to detonate at sea isn't something just anyone can accomplish. Moreover, besides a trace of a clue on the island, there's been no definitive evidence pointing to the perpetrator, which further illustrates their level of organization.
