Despite Sitges' large amount of beaches, for the more extreme water sports it is necessary to look further afield. Water skiing, wind surfing and kite surfing are most likely to be found in surrounding areas like Garraf.
There are all manner of swimming opportunities in Sitges. Whether you have a pool in your hotel, hit the local swimming club or simply take to the waves on the beach.
If you simply want to go for a swim in Sitges, see my guide to Swimming in Sitges - Pools and Beaches.
Sitges has a large Marina area - Port d'Aiguadolç. This is where you will find most of Sitges' sailing services. If you do not own your own boat but would like to be taken out on a boat for the day or learn how to sail yourself, there are many different companies in Sitges offering these services.
For details of sailing in Sitges - both chartered boats and sailing lessons, see my guide to Sailing in Sitges - Advice on What the Nautical Clubs in Sitges has to Offer.
If you plan on getting out on the waves with a jet-ski whilst in Sitges, check my guide to Sitges Jet Ski-ing.
Sitges' microclimate allows for an average of 300 days of sunshine per year giving you the opportunity to be out in the open air, enjoying the water for a good part of the year. Whether you are experienced in water sports or are simply looking for a holiday activity, you should find something that suits what you are looking for in Sitges.