re: Anyone have any experience planning your own excursions at cruise port?

It almost happened to us in the Southern Caribbean but we weren't on an excursion. Got back from excursion with what we thought was time to kill and the clocks on our phones weren't the right time.

We got yelled at for being 15 minutes late (and the port police? picked us up in their golf carts.)

The next day the ship was delayed for about an hour leaving the port because a passenger punched someone before he got on and the police came on board and got him off the ship.

I don't doubt that the ship will leave you if you're not back within a few minutes of the scheduled time.