Lesson learned and a heads-up for others: We bought 2 tickets for 24 hour use on the vaporetto in Venice, at least we thought we did. Turned out that the ticket guy gave us regular one-time use tickets and charged us the price of the 24 hour tickets.
Make sure you look at your ticket at the time of purchase.

Great advice, thanks pdx. I'll definitely keep that in mind for my next visit.

We checked and got the correct ticket, but only were checked one time in three days... locals call them tourist tickets.

Our recent 2-day pass was never checked once or anything said about our extra luggage which they charge more for. Nobody ever checked our 2 train ride tickets or the bus.

Supplementary tip - buy them from machines.

We had to show our 36-hr tickets to officials on one vaporetto.

We were in Venice for three days in October and bought the two-day passes. We were asked to show them three or four times as we were getting on various vaporetti - I had them in a little plastic sleeve on the back of my shoulder bag, so it was easy to flip the bag over and show the tickets. They really did check them carefully to make sure they were still valid.

> Supplementary tip - buy them from machines.

And where are those machines located? I have never seen one. Always bought at counters from people.

Sorry for pdx. But surprised you don't rant and just gave us a useful warning. Very nice of you.

Thanks, kappa. I'm not a ranter. I just go "grrrr" and fume for a moment and think evil thoughts. Then I realize I was a sucker and have to deal with it. Lots of practice.

kappa, I've bought them from machines located right by the landing stages. Couldn't tell you which ones, though - sounds like they don't all have them ?