Suggestions for private water taxi from Venice Airport to hotel near Rialto Bridge

Official water taxi
https://www.motoscafivenezia.com/en/

You can just walk up to the water taxis and take the next available. Same as you would take a car taxi at any other airport. No need to book in advance.

the difference in price for "water taxi" and the private transfer from the hotel is fairly different 50-70 euros. Is there some reason one would use the hotel's transfer vs. the official private water taxi in the website above?

AIfisher, I assume that the hotel’s private transfer is more expensive than the water taxi rate (which is already much higher than the water bus price). This would be a convenience factor. The hotel arranges the transfer for you. It sounds like you can save yourself quite a bit by doing it on your own (as usual). Just write the name and address of your hotel on a piece of paper and hand it to the taxi. They’ll drop you off as close as possible. Be aware that not all hotels have docks, or are on canals, so you still might have a walk.

I should have clarified. yes, the hotel is more expensive. what about the return? Couldn't I just book the return at the time I need instead of the hotel booking it? Just do it online on that website above?

At a first class hotel, it is the desk's job to call for a generic water taxi if you ask for it. Just make sure that the understand you are booking (the day before) an ordinary taxi to be paid to the driver.

Thank you the tips. We decided on a private water transfer for convenience, understanding the price will be more.

I think you will be very happy with that choice. We did the same thing and it was wonderful after a long day of travel to be able to just look for someone with our name when we got out of the airport. It was such a pleasant start to the vacation.

don't be surprised by the long outside distance to the taxi dock from the arrivals hall at the airport. I don't know if somebody will meet you with a sign as you clear immigration and customs, in the arrivals hall, or if you will need to walk to the taxi dock and look there.

If you change your mind, the frequent and very cheap bus is immediately as you go out the door of the arrival hall.

One other question. Is it customary to tip the water taxi driver/captain? If so, how much? (We booked through https://www.motoscafivenezia.com/en/, by the way.)

Nigel commented above about the distance from the Marco Polo air terminal to the taxi dock. There is a moving footpath, it is upstairs, so the walk is minimal.