Looking for a warm beach after 10 day trip to Italy?

May might be just a wee bit early for warm time on the beach - you might get warm sunshine but water on the cooler side for swimming. Early May or late May?

In any case, Sicily, the Greek islands, and many places around the Mediterranean (preferably as far south as you can easily reach) would probably do the trick. Sicily would be a decent choice.

Fly to Catania but the water is problably too chilly

Early May, nah. Late May, possible.
How about a ferry to Rovinj, Croatia? Could you fly home from Pula?
Perhaps the lakes would make a nice alternative if it's earlier in the month.

Crete, the southern shore is warmer.

If you've already bought your return tickets to the US/Canada, where are you flying from? You'll need to be back in that city the night before your flight home. I'd want to go somewhere with frequent transportation links to Venice or whatever is your departure city. A canceled flight could be very, very expensive for you if it caused you to miss the transatlantic flight. I'd be more comfortable with Sicily than a Greek island for logistical reasons, but I say that without having checked on flights between Catania (or Palermo) and Venice.

We stayed in Cefalu (Sicily) early June a few years ago. The water was so cold that very few people were actually swimming. It was fun watching the locals, mostly kids, play in the water but barely above their thighs. In Lipari the beach was quiet and there were alot of jellyfish warnings. This September we visited four Greek Islands and the the water was so crystal clear and wonderfully warm but the sea had all summer to warm up and with only three days the transportation time and effort wouldn't really be worth it.

We lived in Germany for four years and have visited Italy several times. We love Italy, but were not impressed with the beaches that we visited. The Greek Islands would be my choice for going to the beach in Europe.

Also, May in most of Europe will be a bit chilly.

Not only will it be too cold in May, but I also think you need to have a look at what Italian beaches are like. They are crowded, you have to rent an umbrella with a table. Loud, noisy, and nothing like sand beaches in the US. Where we have been for various day trips, the sand was really mud and it wasn't pretty. If you want warm that time of you, you must go very south, such as Southern Crete, Malta or Tel Aviv. Really not worth it for 3 days. Better to spend those three days in Italy, in my opinion.

Be aware that Naples Italy is at ~40 degrees N latitude, roughly the same latitude of New York City. Some other examples are Toronto and Rome are at roughly the same latitude and Toronto and Florence are at the same latitude. Los Vegas and Santorini Greece are at the same latitude.

I don't know what part of the country you're from, but if you are used to beaches in Florida, Venice is far north of anything at the same latitude. If you think you need to rest at the end of the trip, it's an indication you are not planning your trip well. My advice is to throttle back and build in some down days within your trip. If you feel you need to unwind, find something near Venice (assuming you are flying out of Venice) to just kick back. Padova is a 30 minute commuter train ride away and is a charming town. You could go unscripted and just explore.

Im not sure this is the best website to ask about beaches.
Most North Americans visiting Italy do not visit beaches. At most they see the Cinque Terre, Amalfi Coast (Both of which have mostly cliffs) and maybe the Lido di Venezia or the Lido di Ostia (both unremarkable).

I don’t know where Emily went at the beach (maybe Rimini in August) but outside of July and August Italian beaches are neither loud nor crowded. At the end of May, assuming you run into some gorgeous warm weather, they will be deserted. Italians don’t go to the beach in May.
You also don’t have to rent anything. There are plenty of places where there are no beach concessions renting umbrellas and tables. In May there will be none, even at the locations that have many in summer.
There are beautiful sandy beaches also in Italy, or also with cliffs, and they are not mud, but they are far from Venice and the weather in May may not be the best. As far south you go the greater the chance of better weather but no guarantee. May is generally too early, especially early May, even for Greece.
Below a collection of some of the most famous beaches in Italy. There are 5000 miles of coastline in Italy, so the choice is vast. Sardinia alone has hundreds of famous gorgeous beaches.

http://www.blualghero-sardinia.com/it/travel/le-spiagge-piu-belle-della-sardegna/
https://www.skyscanner.it/notizie/piu-belle-spiagge-italia-2018
https://www.viagginews.com/2015/07/15/mare-italia-le-15-spiagge-piu-belle-dove-fare-il-bagno-foto/
https://www.donnamoderna.com/lifestyle/viaggi/italia-spiagge-piu-belle-italiane/photo/Spiaggia-La-Pelosa-Stintino

Hi Carolin,
from Venice you can easily reach the north Tuscany coast and you'll find big sand beaches where to rest and relax; quite different from a Greek Island but still a good choise to chill and enjoy the sun.
You can have a look here:

https://www.visittuscany.com/en/areas/versilia/

http://www.inversilia.com/en/inizio/

https://ptithotel.com/en/

Enjoy your trip!

Thank you so much for all of the very helpful feedback! Really appreciate the time you all took to reply!

From Venice it’s a short train trip to Senigallia, a great little beach town on the Adriatic coast. Miles and miles of sandy beaches and no crowds in May. Water may be a bit chilly for swimming but the beach will be lovely for walking & lounging. Senigallia has great restaurants, including two Michelin starred places. It has a fort & weekday markets. And you can take day trips to the nearby walled hill town of Corinaldo or to the Caverns of Frassasi. I think it’d be a great place to end a trip.

Great idea, Charlene! Don't know why I didn't think of it, since I just went there last year. I just never think about the proximity to Venice as I flew into Ancona, but it looks like they could catch a train and be there in about three hours.

We never heard about the exact time of year, but I was there in late May. I did not spend much time on the beach in Senigallia (LOVE the town), but I did swim in Fano as well as off Sirolo, just north and south of Senigallia respectively.

Great! Thank you for the ideas!!! These tips are so helpful!