There is one main beach event organised annually for students - the Volleyball England Student Beach Cup, and there are numerous other tournaments held over the summer season.
Sadly, we don't have a beach court in Oxford yet, but if you'd like some practice you can try joining our twos' ladder, where matches are played outdoors on grass (using beach rules).
Normally held on a weekend towards the end of May, the Student Beach Cup is an annual event open to pairs from UK universities (both players must study at the same uni). There is also usually a mixed fours event held on the second day. The location of the tournament changes most years, with previous events having been held in Brighton (2007), Margate (2008), and Bournemouth (2009).
Despite there no longer being a beach court in Oxford, our pairs have been highly successful - Hannah Ruddick & Jana Orszaghova won the ladies competition in 2009, the Oxford fours team finished 2nd in 2008 and 2009.
Beach volleyball is an almost entirely different game to indoor. For a start, there are only two players on a team and you use a different ball, and here are some other key rules:
You can find a fuller version of the rules on the FIVB website, or read them here: FIVB Beach Rules and diagrams.
One more aspect of the game that is not used indoors - hand signals. This explanation is taken from Exmouth Beach Volleyball's website (who have a nice section explaining various parts of beach volleyball). The most commonly used hand signals are:

