If your train stops at Maestre, there are lots of other trains that continue on to Venezia Santa Lucia (sometimes seen as V.S.L). But first make sure your train won't do the job for you.

europeforvisitors.com/venice/articles/venice-railroad-station.htm
has all sorts of things you might find useful if you decide to go by train.

Once at VSL, exit the train station out the front and down a very wide set of stairs. You will see lots of boats (vaporetto) right in front of you. You can find one of them to take you to San Marcos or you can walk there in 5 or 10 minutes.

I suspect another boat would also take you from VSL to the Hilton, but I don't know the details of it. Venice guide books usually have maps of the water transport routes. I couldn't find a web one big enough to be readable.

Romelle