So is that reason why the current "beer" tastes watery cause fermentation hasn't completed?
It tastes "watery" because you are tasting it while it is still in the fermenter, it is GREEN and UNCARBED, and is not a true represntation of what the beer will be like when it has carbed and conditioned.
Also, it really is hard to judge a beer until it's been about 6 weeks in the bottle. Just because you taste (or smell) something in primary or secondary DOESN'T mean it will be there when the beer is fully conditioned (that's also the case with kegging too.)
The thing to remember though is that if you are smelling or tasting this during fermentation not to worry. During fermentation all manner of stinky stuff is given off (ask lager brewers about rotten egg/sulphur smells, or Apfelwein makers about "rhino farts,") like we often say, fermentation is often ugly AND stinky and PERFECTLY NORMAL.
It's really only down the line, AFTER the beer has been fermented (and often after it has bottle conditioned even,) that you concern yourself with any flavor issues if they are still there.
I think too many new brewers focus to much on this stuff too early in the beer's journey. And they panic unnecessarily.
A lot of the stuff you smell/taste initially more than likely ends up disappearing either during a long primary/primary & secondary combo, Diacetyl rests and even during bottle conditioning.
If I find a flavor/smell, I usually wait til it's been in the bottle 6 weeks before I try to "diagnose" what went wrong, that way I am sure the beer has passed any window of greenness.
Lagering is a prime example of this. Lager yeast are prone to the production of a lot of byproducts, the most familiar one is sulphur compounds (rhino farts) but in the dark cold of the lagering process, which is at the minimum of a month (I think many homebrewers don't lager long enough) the yeast slowly consumes all those compounds which results in extremely clean tasting beers if done skillfully. Ales have their own version of this, but it's all the same.
Carbonation will go a long way to giving you the perception of flavor, and body, you really can't judge your beer until it's been bottled, carbed and condition. At this stage your beer is uncarbed and green. The presence of co2 alone will go a long way in improving the flavor and mouthfeel of it.
Your beer has a journey to still go on. You really don't need to do anything to fix your beer. More than likely there is nothing wrong. Just bottle it, give it a minimum 3 weeks to carb and condition at 70 degrees, and I betcha you will think you were silly for worry about this at this stage, like just about everyone else who has started a thread like this.
I don't bother to taste my beers anymore until they have been in the bottles for at least 3 weeks, often more. I've found it is a waste, I won't get a true picture of the beer until it's been carbonated and lost the greenness anyway. And there really is nothing I could do to "fix" it anyway if I thought there was something wrong, which there rarely is anyway.
Time is your friend.
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