After walking through what looked like a warehouse district, we found a small cardboard sign directing us to the check-in area. We were the only ones in the hall since we arrived well after the main rush. The clerk looked at us and somewhat indignantly stated "Oh, you have your luggage, you should have left it at the yellow tent." We did not see a yellow tent and there was no one outside to direct us. My reply was a terse "There was no one there." His supervisor then tried the same admonishment to which my hot, sweaty, tired, reply was an even more terse "I said, there was no one there." They got the hint did not push the issue and checked us in promptly.
Once on board, we were able to shower change and eat. We did not venture out again our first evening in Venice. On our second day we did a walking tour on our own that took us through the Jewish Ghetto, St Mark's Square, and plenty of points in between. My advice for Venice is to stay away from the tourists and follow the locals, they know better.
I was a little disappointed that Holland America had not arranged some water taxi service directly to St. Marks, Guideca and/or Lido. You either needed to walk from the terminal or arrange your own transport. A previous cruise did have a shuttle service to take passengers directly to St.Marks. There was an extra charge of $10, but it was worth the charge having used it about 6 times.