for fishing, you can go sealine, and khor el ludaid, dukhan beach, wakra beach,
I wish to know your inclination to guide you to the area where u can be enjoyed in vising the place. Carefour, there are three outlets, one in corniche, other in villagio, third one in the landmark. there are lot of shopping interesting places are there in this three significant business complex I recommended to you.
Well, if you want to go for relaxing somewhere in the sea side, you can go Al Gharia, and Al fuwairet, Al huwailiya, and Dukhan beach side and enjoy the swimming and all that free of cost.

The third one is hotels, and Admiral club in Ritz carlton in thursday night is much interesting, QR. 200/- admission fee.

There are many fitness clubs and other entertainment areas in Qatar you will find seperately existing in all over Qatar. Unless I knew your trend, and interests, I am unable to assess and provide you in here right direction you look for. Anyway, Good luck, and please feel free to ask further matters that confuses you in visiting any exiciting places in Qatar.