Peregrina: Thank you for your warning about lack of date. My bad. The accompanying traveller's story was written in 1999, very much out of date. Of course, one should get updated information from the company running the service before relying on it.
CC Wine Lover, we are booked on the same Viking Saturn cruise as you from Barcelona February 2024 with a three day turnaround in Venice and have been following on the roll call. There is a bus service Chioggia to Venice (arrivaveneto.it) with a current website and timetables. Travel time (no doubt traffic dependent) is estimated slightly less than the ferry Fieldofdreams mentioned. We are considering spending one night in a hotel in Venice, returning to the ship on day 2 of the turnaround.
I'm keeping options open as I understand there is only one dock in Chioggia and, if it is occupied, Viking Saturn will be redirected to the industrial port at Maghera or somewhere even further away from Venice. Or it may move berths sometime during the turnaround.
As I said before, I hope cruisers on this route will post their experiences very soon.