Is there a underground bridge from Florida to Puerto Rico?

Answer 1

No. Puerto Rico is about 1000 miles (1610 kilometers) east-southeast of Florida. For reference, if you were to go the same distance in the opposite direction, you'd end up near New Orleans, Louisiana.

Building a 1000 mile tunnel (underground bridge) would be financially cripling, not to mention, an engineering feat of astronomical proportions. The longest proposed tunnel would be in China between Dalian and Yantai. If completed, that tunnel is expected to be 123 kilometers (76½ Miles) long and cost a minimum of the equivalent of $40,500,000,000 U.S. dollars. For reference, that sum is the same as the total amount of money proposed in the 2014 U.S. federal budget for road, rail and airport repairs and maintenance, including improvements for the entire country of the United States.

A more economical way to build a road or railway link between Florida and Puerto Rico would be to build a bridge or tunnel from Key West, FL to Santa Cruz del Norte, Cuba (96 miles - 155 km), another bridge or tunnel from near Punta de Maisi, Cuba to Presqu'ile du Mole, Haiti (about 53 miles - 85 km), and a third 71 mile/114 km tunnel or bridge from near Punta Cana, Dominican Republic to Rincón, Puerto Rico. The third bridge/tunnel could use Isla Mona, PR as a "halfway point" but that island is a nature preserve.

But even this would mean that three tunnels each twice the length of the longest under water rail tunnels in the world (Tsugaru Strait - 33 miles, and English Channel Tunnel - 31 miles) or the longest bridge over water ever built (Lake Pontchartrain Causway - 46 miles) would have to be built.