You have two options available. The water bus service from the airport called Alilaguna does not stop at the San Toma terminal, so this is not a viable option. You can take a private water taxi from the airport to your hotel, but be aware that this is the most expensive option. You could try a shared water taxi to perhaps cut the cost. For a private water taxi, you would have to book this in advance online.
The other option is to take the bus or a taxi from the airport to Piazzale Roma. Piazzale Roma is the end of the line for land transportation arriving in Venice, from here you travel by boat or by foot. From Piazzale Roma, you can take the Vaporetto, Line 2, and get off at the San Toma terminal. Your hotel is just a few minutes walk from the terminal.