'Ploce Gate Beach'
Go down to the Ploce gate and turn left. Just after you pass the series of buildings and courtyards that used to be the quarantine facilities on your right you will find steps down to a pleasant sand and stone beach. This is our closest swimming spot and will take no more than 10 minutes to walk and is a great beach for kids.
'Monastery Bay'
If you have the time and energy continue on past the beach above and walk up the gentle hill past the Argentina Hotel. On your right a street will head off slightly downhill following the line of the coast. Here you will pass beautiful parks and many lovely villas.
At the end of the street is a Monastery and if you go around to the left of the Monastery you will soon find a set of steps leading down to a magical stony beach.
Here you can use your towel or hire a lounger and there are a couple of bars selling drinks.
Alternatively, there is a small boat that will take you to this beach from the Old Port (in the Old Town).

'Hole in the Wall'
A fun place to swim - go down into the Old Town and walk across to the wall on the far (seaward) side where you will find a small gate (we call it the ‘Hole in the Wall’). This leads you onto the rocks outside the town wall.
There are lots of places to dive or jump in and a ladder to help climb back out. This is not the best place to go if there is a swell running so check the state of the sea before heading off. There is also a bar providing drinks.

Cavtat
If you have a car or are happy to take a bus, then make your way east to Cavtat.
To take the bus:
At the bottom of the steps leading to Villa Antipodes, turn left and walk about 100m up the road where on the right side you will find a bus stop. Catch the number 10 bus for 10 kuna per person and in 20 minutes you will be in delightful Cavtat.
You can wander through this special seaside village with its beautiful bays and past an impressive array of super yachts and then continue on around the peninsula to your right where there are several rocky and stony beaches suitable for swimming and relaxing.
Remember that Cavtat is the ancient home of the founders of Dubrovnik and was once a famous centre of healing in Roman times.
Lokrum
Another option is to take a ferry to the island of Lockrum and explore and swim
There are a lot more options, however, these are ones we have enjoyed.