It appears that no one ever answered this question, and you may have found your answers elsewhere, but I thought I'd speak up!
There is no beach near Universal Studios or near the Burbank airport -- they are both quite a bit inland and not right near the coast. The nearest beach, distance-wise, would, I guess, be Santa Monica Beach -- and it's not quiet in the least bit. There's lots of activity there, and the Santa Monica Pier is right there, which is fun. The quiet beaches are further up or down the coast. I don't know if you'd have a car or would be relying on public transportation, but if you use public transportation (buses) it could take you a good 45 minutes to one hour to get to SM Beach from Burbank, possibly longer. If you are using a car, it could take 30-40 minutes to get from, for example, Universal Studios to Santa Monica Pier.