Transport options San Marco to VEN

The airport codes are VCE and MUC.

Check the Alilaguna
http://www.alilaguna.it/en/lines/line-timetables

Stay at a hotel by the airport the night before.

Gail, There is no airport code "VEN".
MUN = José Tadeo Monagas International Airport Maturín, Venezuela

From your mention of St Marco, I am guessing you mean Venice Marco Polo Airport (VCE) to Munich airport (MUC), which IS NOT a domestic flight.

"Is it possible to get from San Marco & arrive the airport for 5:30a.m?" - St Marco is the opposite end of Venice to the station and Piazzale Roma (where the buses leave from). So you would have a long walk before you could get a bus (too early for Vaporetto).
And, 05:30 departure means ~03:30-04:30 at the airport, I am not sure buses run that early.

If you cannot afford a private water taxi (do they even run that early, it would be dark?), then I think you would have to stay at the airport.

Yes, the private water taxis do run that early - but you will pay dearly for that ride because it's out of the normal operating hours.

BTW - there are 2 airports for Venice: VCE (Marco Polo Airport) and TSF (Treviso Airport). VCE is the one nearest to Venice Island.

a 7:30 flight won't need more than a couple of hours ahead. There are number 1 night vaporettos from S Marco to P Roma all night. Which end of S Marco will you be? You could get the first bus from P Roma and should have plenty of time.

Assuming by VEN you mean Marco Polo Airport.

I would be looking for a hotel by the airport

The first boat for Alilguna leaves S. Marco at 03:50 or the next one an hour later.
http://www.alilaguna.it/en/linea-blu/blu-timetable

Thank you all for the info. Sorry about the airport code - I meant VCE. We arrive Venice for 2 ngts with a tour group & our hotel is near Piazzale Roma. RS review of that hotel is good, but he notes the area isn't the best. We have 2 ngts on our own in Venice after the rest of the tour departs. We kind of wanted to stay where the action is, but may have to re-think that. I don't really want to move from the tour hotel to San Marco for only 1 ngt & then move again for the last ngt. After a tour & all it's moving around, I'd like to stay in 1 place for our last 2 ngts. Does anyone have recommendations on where to stay for easy transport connections to VCE but also convenient for exploring Venice while we're there on our own? And we're on a very tight budget too. Thanks again!

Thank you all for the info. Sorry about the airport code - I meant VCE. We arrive Venice for 2 ngts with a tour group & our hotel is near Piazzale Roma. RS review of that hotel is good, but he notes the area isn't the best. We have 2 ngts on our own in Venice after the rest of the tour departs. We kind of wanted to stay where the action is, but may have to re-think that. I don't really want to move from the tour hotel to San Marco for only 1 ngt & then move again for the last ngt. After a tour & all it's moving around, I'd like to stay in 1 place for our last 2 ngts. Does anyone have recommendations on where to stay for easy transport connections to VCE but also convenient for exploring Venice while we're there on our own? And we're on a very tight budget too. Thanks again!

And to add some clarity, our flight leaves VCE @ 7:30am so we would need to be @ VCE for around 4:30-5am. Thx again.