Sailing is cracking fun, there's nothing like watching one of your mates get a bit overconfident in his tacking and jibing and then dumping himself in the drink. As well as this being great fun it's the ideal way to find if sailing is for you - next stop the Bahamas!
Generally, the instructors will be teaching you the basics and ensuring you don't drown each other but apart from that how serious you treat the whole affair is up to you.
Suggested alternative or complementary activities: windsurfing, kayaking, canoeing, yacht sailing.