The answer is yes, a decal is required to visit the bahamas
or any country with a pleasure craft over 30 feet. The process can take almost 6 weeks to get the decal and you will need the number if you want to apply for a local boaters option when returning, the local boaters option is a must if you don't want to personnally go to the customs
office to check in upon your return.
The decal cost $27.50 and is renewed once a year. Also note that if your boat is over 35 feet you will have to pay $300 when you enter the Bahamas.