Are you just randomly Googling?
The St. Johns does not pull from as far south as Boca, that's just nonsense. The St. Johns starts between Yeehaw Junction and Vero Beach. Everything on the east coast from Lake Okeechoobee and southward flows southeast.
There's basically a ridge that runs approximately along the Turnpike. There are rivers on the west side of the Turnipike, all the way up to Central Florida, that flow southward. The Peace River starts around Bartow and empties by Punta Gorda/Port Charlotte. The Everglades "river of grass" officially starts in Kissimmee.
On the east side of the Turnpike, until the Turnpike gets very close to the east coast around Fort Pierce, rivers go north and/or east, such as with the St. Johns.
In SE Florida, you have short-distance rivers like the Loxahatchee aned the St. Lucie that flow south and/or east to the Atlantic.
Unless that you are saying that all the water from Boca magically flows north, jumps over the Loxahatchee and St. Lucie Rivers, and then joins up with the St. Johns up in Yeehaw Junction. That would be impressive. Maybe Del Boca Vista Phase 2?