The Tenders were free the last time we were in Belize...it's a 4 or 5 minute ride and goes pretty fast...unless there are waves....The paid tours (booked from the ship) are first to go off...but there are a number of tenders coming and leaving....Some ships will use their own lifeboats as tenders too....but NCL didn't at the time I was there...There is shopping and dining as you get off the tender....Downtown Belize City isn't much....Take one of the excursions...Belize river, mayan ruins, cave tubing.....Happy Sailing..
NCL is not allowed to use their lifeboats in Belize as tenders and they are required to hire out the tenders. They are large boats with capacity for about 200.....they come back and forth about every 10 minutes. If there are long lines for the tenders ....NCL will hand out tender tickets....they are no charge. As Berick has stated the tours go off first. If your not on a ship excursion, then after about 2 or 3 tenders you should be able to go to the gangway and just hop on. It's very easy and quick to the Belize pier.
To add what the others have said, you can get tender tickets at the locale reported in the Freestyle Daily. After all the tours have left, you will not need a tender ticket.
The line forms early, if you're in no hurry, just wait for the line to dissipate, you'll will not have to wait in any lines.