Hi Divya, There is this place call Srivardhan on the Konkan stretch and close by is Harihareshwar. These places are a little offbeat but the beaches are super clean unlike the ones in Mumbai. So if you want to just relax, I suggest go check out these places. You will allsoo get water sports and activities at a nominal rate. I have posted a trip about Srivardhan and also photo blogs.. Can check those out. Enjoy!
Here are some popular places to visit near Mumbai:
Last month I have visited Kolad with my buddies. River rafting is one of the best thing i have done in Maharashtra. You can rent a car at affordable prices from https://www.avis.co.in/ to explore all the places near Mumbai and Pune. It will save your time.