For me Guardalavaca in Cuba was paradise. Clear warm water, coral reefs to snorkel around, great long beach and perfect dive spots.
I guess it all depends on the person - someone I work with will only ever take city breaks to places like New York & Tokyo. To me those places are hell on Earth - to him Guardalavaca would be.
For me a quiet beach and preferably surf make a great vacation. I'd take warm water and warm weather over cold but thats because I come from the UK and spent March freezing my balls off in the Atlantic Ocean in full wetsuit gear including a 3mm hood, boot and gloves....ummm minus 1 - great weather for surfing!!!