When you leave Canada
or the USA you will not get an exit visa unlike many other countries. Regardless, your entry to the US from Canada
will be recorded.
The Bahamas Customs
will issue you a Cruising Permit
upon entering, provided you pay the appropriate fee in cash. Your permit
will be good for perhaps 60 days or more. It depends on the Customs
agent. Ask for 180 days...you might get lucky. Renew as needed.