Just few info from Venise we visited in August this year:
There are several marinas
and venise island is a small one, so even if you cannot use your own tender
you will not be very far away from everywhere in the city.
You can rent open boat with outboard
engines at "Brussa is boat" (Google it), otherwise you have plenty of different ways to travel on the water
Vaporetto: public transport / water
coaches, you can buy passes for 1 day or more and go absolutely everywhere, including all the surrounding island of the lagoon
(Lido, Burano, Murano...), they are very frequent but also overcrowded in the middle of the day.
Motoscaffi: individual water taxis, more expensive, 70 Euros to go from Venise (San Marco) to Murano for example, we booked one with our hotel
to come from the airport
170 Euros including the transfer from the terminal to the port with private van.
The gondola: although this is not a transport to go from A to Z, this has to be done once at least...quiet expensive as 1 hour can go from 150 Euros to 250 Euros...but who can miss it?
The tragheto: this is a gondola that crose the canal (the main one), carrying several passenger at some location in venise, few Euros for the crossing.
The idea to use our own tender was a good one until we arrived in Venise amd realized how busy is the traffic, how narrow can be some canals and how easy it is to visit the place with the other means of transport.
The crowded water coaches are empty early in the morning (let's say up to 08h00 am) as well as the end of the afternoon (around 17h00 - 18h00 pm).
Once you are onshore, the feet are the only way to move, but again Venise is a small place that can be crossed effortless by foot.
Apart from the marinas, they are various places where (super to mega)yachts are moored, quayside.
I noted that although the lagoon is large, they are canals established and I do not know if you must stay in these canals or if you can go outside them for sailing purpose.
In the mean time the depth
in the lagoon must not be very deep and ensured at location outside the well identified canals...some place are very narrows not to say that the sand reach the surface.
On a touristic point of view:
We visited 2 of each Venise district everyday (or 1 district and 1 island).
1 week is a minimum if you want to seel all of them and have the time to see some museum.
We took 5 days overall but only wandered the places.
We took around 200 pictures a day as each corner is appealing.
The maritime museum is only open in the morning and we recommand it.
Burano and Murano have to be on your list...Lido is less interesting, you can skip it if you have no time.
Each venise district has its own charm and character, we used the "Lonely planet" guide, out of 3 others, this was the best one to visit the place (guided tours are clear and really spot on to not miss anything).
San Marco place is nearly empty if you go before 08h00 am, after it is madness...
What can I say....Venise is magic, simply magic and surely one place to see in once a lifetime.