OK, I get it, it's not a beach, it's an entire islet.
First of all, let's get the name thing out of the way. People on Korčula mostly call it Sutvara, Google Maps calls it Sutvara, but historically, it has been called Sitvara, as you can see, for instance, on korcula.hr website, so I'll call it Sitvara for the purposes of this article, fully aware that today almost everyone else calls it Sutvara. Call me old-fashioned. Call me a sucker.
It's an islet in the Korčulan archipelago, not one of the closest ones to Korčula, it is definitely one worth exploring. If you're anywhere near Korčula on a boat of any kind, it is my suggestion that you make it over to Sitvara for a relaxing afternoon, a swim, some down-time, a walk, a swim, a surprise...
On the northern side of the islet, you will find some rocky slabs, getting down to the water perfectly, helping you to get in and out of the sea, nice, gentle, inviting, smooth because of the winds that worked on them for years. On this side of the islet, there will be shade during the afternoon, as there are trees on the islet helping you get your rest. During the busiest days of the year, there will be other people there with their boats as well, but there's just enough shade for everyone to enjoy, and swim in the perfect sea right in front of you.
Very near to the norht-facing side of Sitvara, there is a smaller-still islet. It's tempting to swim to it, I know, just be careful. Once you get there, you will not be able to get on it without any footwear on, the rocks there are so sharp, and once you do, you'll be disappointed, as there's literally nothing on there, except the sense of accomplishment, that you managed to get to it! And, of course, an amazing view of the position where the best of the best of Plavac Mali vines are planted.
But, you should walk around the islet! On its western-facing side there's an actual beach. It's not big, and the pebbles are quite large, admittedly. But, still, it seems like something Terry Pratchett would've written about, with its perfect view of Badija and amazing sea and the sense of being - elsewhere. There's some shade above the beach, and in the morning hours the entire section of the island will be shaded, so there's really no excuse not to enjoy it fully.
If you decide to walk up from the beach a bit, you're in for a surprise, as there's a house there! There used to be people tending to sheep on the islet, and extracting stone, and at some point in the past someone decided to build a weekend-house there, and it still stands today. There's really not much there at all, but still, it's kind of interesting to see a building of this size in the middle of an islet - too bad it has not weathered more nicely, and hopefully some day it will serve some purpose, instead of just sitting here and deteriorating.
And, if you follow a narrow foot-path down to the coast from the house, and walk to the southern-facing side of the islet, there's another surprise for you: another little beach! This one important because it's shielded almost fully from the afternoon maestral, recently nicely cleaned and welcoming to any boats that might come here for shelter and a very pleasant afternoon. I have no idea who built the wall there, or why, or why it's gotten into the bad shape it's in today, but still - there's a man-made wall just above the beach, and it's amazing! This small beach is facing south, so there won't be much shade at any point during the day, but it is one of the nicest places to spend your afternoon on a boat, if docking close to the shore and swimming in perfect sea is your thing.
On your way, you will see the rocks of Sitvara, formed over the years by the sea and the winds - perfect sea, rock and wind art, if there ever was such a thing!
Just a word of warning: if you decide to go to Sitvara, and dock your boat on the "wild", north-facing side of the islet, beware of the maestral in the afternoon. If you're not careful, you might end up in some trouble, unable to get back to your boat safely and struggling to get away from the islet. If you feel any Western wind, it's the time to get onto your boat and away from that side of Sitvara, as it is fully open to maestral coming from the Pelješac channel and being at its peak there. Don't get yourself in the situation where you need to carry your stuff across the islet to the southern beach, to be able to safely get onboard your vessel.