Here, we'll work with multiple layers and layer masks to selectively blurand sharpendifferent parts of an image.
Here's my original image.
Press Command-J (PC: Control-J) to duplicate the Background layer. To this copied Background layer, apply some form of blurring (under Filter>Blur). In this case, I used Motion Blur, since my photo had some motion in it. Lower the opacity of this layer to lessen the effect slightly.
Make a selection of the area that you want to be blurry. Here I used the Lasso tool (L) to make a basic selection of the water.
Since I only wanted the main edge of my selection to have feathering, I didn't apply feathering to the entire selection. Instead, I pressed Q to switch to Quick Mask mode and made a rough selection around the edge of the mask. Then I applied a Gaussian Blur (Filter>Blur>Gaussian Blur) to the mask, in effect applying feathering to just that edge. Press Q again to return to Standard mode.
Click on the Add Layer Mask icon at the bottom of the Layers palette to mask the area you don't want to be blurry (i.e., to hide the blurry layer in that area).
Duplicate the Background layer again and apply the Unsharp Mask filter (Filter>Sharpen>Unsharp Mask) to the copy. These are the settings I usedyours may well be different, depending on your photo.
Press-and-hold the Option key (PC: Alt key) and click-and-drag the layer mask from the blurry layer to this sharpened layer. That will copy the layer mask, but we need the mask to affect the opposite part of the photo, so press Command-I (PC: Control-I) to Invert the mask.
Here's the result.
In this example, I didn't have a specific area I wanted to be blurry, so after duplicating and blurring the photo, I added a layer mask and used the Gradient tool (G) on the mask to gradually fade the blurry area. Then I selected several areas that I wanted to be slightly blurry and filled them with either a gradient or 50% gray.