I'd second Jaguar in the Grove (try the ceviche) and Monty's (for fun marina atmosphere).
I have to disagree with The Chart House. The food there is terrible - no water view could fix that.
For very expensive but terrific Italian with great wine, Casa Tua on South Beach is my favorite. Had a great bottle there last time (I think it was Montepulciano or Montalcino - always confuse those - from Australia). I think you can go there for drinks only and sit in the back outside, which could be a nice option if you're not looking to spend a bunch on dinner. No water but it's a very elegant atmosphere.
For solo dining in particular, my thoughts would be:
Jaguar (Grand Ave. just off intersection w/ Main Hwy)- I recall there's a nice bar area to sit, ceviches are great, other stuff is pretty good as well.
Scotty's Landing (off Bayshore Dr by the convention center) - I'd stick with beer over wine and the food's not great either, but a nice place to hang out and sit outside, look out on the water (there are surprisingly few places actually on the water in Miami, believe it or not). Mony's is similar, their peel & eat shrimp are decent.
Ideas (Bird Ave. / 27th Ave.) - Interesting and authentic upscale Spanish. A really peculiar wine list limited only to wines from Castilla y Leon - which if you like Spanish reds works out OK, since they've got a nice selection from Rioja, Ribera del Duero, Toro & Bierzo. Probably not a great place for solo dining (no bar, only tables, and somewhat quiet as it really hasn't caught on here yet).
El Carajo (CITGO station at 17th Ave. & US1) - fantastic little tapas bar in the back of the gas station. Get the piquillos stuffed w/ bacalao. Take any wine off the shelf (very good selection) and pay $15 over retail.
In Coral Gables (not more than 10 minutes by car from Coconut Grove where your hotel is) there's several other options. Among the best:
Ortanique (on Miracle Mile) - nuevo caribbean, noisy place, serve the ful menu at the bar, excellent wine list.
Chispa (225 Altara Ave., nr US1 & LeJeune Rd) - nuevo latino, also a noisy busy place, pretty sure there's a bar area to sit at.
Copas y Tapas (Miracle Mile) - little Spanish tapas place with a decent selection of Spanish wines including several by the glass (incidentally there is an excellent wine store right down the street, Wolfe's Wines, which if you are a wine person you'll definitely enjoy
Su Shin Izakaya - Japanese place on Aragon Ave. (one block off Miracle Mile). Decent sushi and some really interesting other cooked dishes, done tapas style, with several blackboard specials daily.
jaguar around the corner from you...no water, but the heart of the grove with wine nights. jaguarspot.com
scotty's on the water near you too...not sure about the vino there? casual.
chart house-yes it's a chain, but it is on the water and has a decent list for vino with good food. practically across the street from GB.
balens-also on the water and should have the best vino and cuisine of them all, well maybe with the exception of the ceviche nuevo and other delicacies over at jaguar.
cafe tu tu tango is great too...heart of the grove for world apps and vino.
cefalo's wine cellar just opened and from what I've heard are definately trying hard to work out the kinks. plenty of vino, that's all I know. south grove main hway.
ideas-no water spanish haute cuisine and vino from castilla y leon, Espana
citgo gas features the best vino store in dade with few exceptions. take a retail bottle to the hotel or have some with their spanish tapas.
17th ave and us1.
monty's is a nice waterfront vibe too...or at least it used to be.