Kos Island has been blessed with a multitude of beautiful beaches.
Generally, the beaches of the north coast are often windy and lined with pebbles, while the ones at the south are sandy and sheltered from winds in the summer.
Marmari beach is a long sandy beach, backed by sand dunes, in front of an long line of hotels that have segmented it into areas of chairs and umbrellas for their patrons. The beach is so large though that there is ample space for independent swimmers to find a quiet spot. When we visited the sea was too rough to swim, and there was a black bar of seaweed that covered the surf near the shore. Signs on the beach explained that the seaweed is part of the natural habitat, so we assumed this is a permanent feature of the beach.
There are actually two beaches framing the man-made port of Limnionas. One beach is too windy while the the other one (protected) a bit too murky. Neither beach seemed very appealing. Limnionas beach is a bit out of the way and Ag. Stephanos or Paradise Beach might be a better choice if you are in this part of Kos island.
Another out-of-the-way beach that offers great scenery and beautiful sunsets but it's often too windy and rough. Great restaurant on the hill to have dinner overlooking the sunset.
The hot springs is on our list of places to go in Kos. The beach itself is not much to write about, but the little hot-tub enclosed by the rocks is very pleasant even when it is very crowded. Drive down a rough gravel road and park near the hot springs. The signs at the Cantina at the top of the hill make it sound like everyone needs park there and to walk down to the beach(for obvious reasons), but there is enough parking below. The road down is a bit precarious, but this way you don't have to climb the steep dirt road back to the top on foot.
All these beaches are really one long stretch of sand, divided here and there by a rocky outcrop. They all share the same crisp water and soft sand. Choosing either one would be a good choice for a nice swimming experience.
Hard to rate this one because it is taken over by nudists and anyone approaching the straw umbrellas is immediately stared down by groups of old naked men who stand up and make sure everyone sees their private parts. This doesn't make the beach a very appealing place to hang out, and since there are no signs declaring its nature it can be a huge surprise if you happen to venture there with your family. Beyond the umbrellas there is a long stretch of sand that has remained undeveloped where one can find some space. It is lined by soft sand, and it's backed by very large sand dunes. If naturalism is not in your plans the nearby "Magic" beach is a good choice to swim.
Magic Beach is very nice, relaxing and not too crowded. The beach is very wide and lined with soft sand. The water is cold and the beach slopes abruptly toward the deep end, so it might not be a good beach for children. One must enter the water through some very large an slippery rocks, but the water is fantastic. There is a restaurant at the back.
Paradise Beach is the last beach in this long stretch of sand, and it's maybe the best of the group. It is lined with fine, golden sand, clean water and a sandy sea bed that slopes gently and remains shallow for a while. Nice rocky area at the western end is great for snorkeling. It does get a bit too crowded with parasols and people, and it has a restaurant, and a variety of water sports.
On the north end, someone bulldozed part of the hill to make room for a few umbrellas and a kiosk where you can pay to use the large inflatable playground that floats offshore. It looks kind of bright but it's a lot of fun, for children and adults alike.
Kardamena is the most "touristy" part of Kos, and its beach is a good place to swim. The narrow part of sand to the west of the town is too close to the main road but more quiet, as the beach gets more crowded near the town.
The beach in front of Club Med and to the west of the basilica is very nice. It is sandy and not too crowded, although it definitely feels like it's part of the club. By law all beaches in Greece must be accessible to everyone, so if that's where you want to swim, feel free. The beach to the west of the ancient ruins is also very nice and the Kastri islet in the middle make it very picturesque.
Kamari beach is the patch of sand and large pebbles in Kamari town. It is popular by windsurfers and lined throughout by restaurants, and cafeterias.
The "beaches" along Vasileos Georgiou road (south of the port) are not very appealing. Maybe years ago they were adequate, but today all the sand has been eroded away. What you will find there are man-made, narrow patches of sand, too close to traffic, that are sustained with sandbags. A little further south along the same road, after the marina, there is another sandy spot that might not be a bad place to swim if you are stuck in Kos town without a vehicle.
The beach alongside the northern end of Kos town is very crowded and it is framed by the most touristy, and least appealing part of town. The sand is soft and the water is clean though, so if you are looking for a place to swim in the city and you can ignore the party crowd this might be a good beach to visit.
Lambi beach is located at If you find it calm it must be a nice beach. Sand, wide, backed by sand dunes and a bicycle road. As it is it was too rough and way too windy to swim.