Aqualand Cap d'Agde
This is a fun park based around water and with three levels of attractions, there's something for everybody. Even teenagers - perhaps especially teenagers! - think it's cool. So if you or members of your family are adrenalin junkies there's the 'Black Hole' or the 'Niagara' which offer heart-stopping drops and curves that defy what you learnt about centrifugal forces at school.
For more general family fun, try the Anaconda or the Rapids, and little kids will be thrilled to be let loose in the Children's Paradise. Everything is built in, on, through or under water, so all you need is your swimming costume, towels, sun cream, hats and sunglasses. There are several self-service restaurants offering a grill and various fast food alternatives; 'haute cuisine' it is not but the kids won't want to hang around the table too long - they'll be wanting to get on and try out the next attraction.
You can find just about anything here for your waterpark needs; there are slides, rapids, bubble baths, and there is even a beautiful island covered in grass and surrounded by palm trees where you can lie back to catch some some rays. There are 'mascots' to have your picture taken with and there is even a photographer who garlands you with flowers and perches a parrot on your shoulder, camera at the ready, to snap away and capture the moment!
There are other Languedoc-Roussillon Aqualand parks at St Cyprien
and Port Leucate if you are based further south than Agde
. Free parking.