Someone may have mentioned this, and I missed it, but there are 2 cruise terminals in Venice, Marittima (for large ships) and San Basilio (for small ships and megayachts). I don't think the OP specified which one they are using.

Thanks for that reminder, Delaine - I've worked out that we'll be leaving from Marittima. Di

Stazione Marittima means just Cruise Terminal.
But all BIG cruise ships leave from the place everybody referred to.

Neckervd,

I realize that all big ships leave from Marittima, but all cruises are not on big ships, and OP didn't specify the size of their ship. Thus, you couldn't automatically assume it was a large one. I took a small ship cruise (280 passengers) that left from San Basilio.