Possible Clues:

• Port-of-Spain's island
• Caribbean isle
• Island near Venezuela
• Island criminal group covering racket up
• Columbus landfall of 1498
• Air didn't, train did — and those swimming could get here repeatedly
• Setting up racket in gangster's organisation from island
• Criminal group concealing racket over in Caribbean island
• Island group keeping the noise up
• Southernmost island in the Caribbean