Deep Water Bay is not the most beautiful beach in Hong Kong – but it is so easy to reach. It is just on the other side of the Aberdeen tunnel, and takes less than 15 minutes to reach from Causeway Bay. Minibus 40 is a quick and good option, otherwise taxis will take you there.
This is one of the few beaches that are open all year round, with lifeguards on duty (between 8am-5pm from November to March, otherwise between 9am-6pm).
It is only a few steps from the street away (hence very accessible but the downside is that you can hear and see the traffic too). It has changing rooms, toilets and the Coconuts Bar/Kiosk next to the road has a few drinks and snacks in store. So it is very convenient.
During the week it is fairly quiet – it gets crowded during the weekend though, especially on Sunday all the BBQ pits are busy from the early morning hours. If you go there on weekdays, it is quiet and just a few people will be swimming or relaxing.
There are no rocks, just plain sand and hence it is easy for kids to access and play in the water. But depending on the weather (especially if there have been storms recently) the water will be muddy and cloudy, not as clear as it might be at other beaches. Still, it is a nice beach and a good option if you do not want to drive to Repulse Bay or Stanley.
You could also hang out a Deep Water Bay first, and then head over to the BBQ pits and from there walk leisurely along the promenade to Repulse Bay. It is not far and a flat, easy walk that last maybe 30-45 minutes depending on your walking speed.