(This post is written for those who may not be experts, and don't know how to make texture packs.)
Building underwater bases is great, especially near the new underwater fortresses. But the water animation against glass makes it difficult to see through, and so you cannot enjoy the view very well. Optifine settings don't help, either.
There's an easy fix if you can manage a graphics program. You want to edit a file named water_flow.png. To find this, go to:
C:\Users\yourname\AppData\Roaming\.minecraft\versions\1.8.1\1.8.1.jar (the version number will be different, depending on which you are using.)
Right click the .jar file and open with WinZip, WinRAR, 7zip or whatever archive application you have.
Navigate within the .jar file to: assets\minecraft\textures\blocks
Click the file water_flow.png and extract it to your desktop. Do NOT edit the file water_flow.png.mcdata. Don't close the archive application, leave it open.
Using your graphics program (Photoshop, etc.) open the file and adjust the transparency to at least 50%. This will make the water clearer, without losing its bluish color. If you need help on how to adjust transparency, check the help files in your graphics program. Save the file.
Now find the file on your desktop and copy it to the clipboard. Go back to your archive application, which should still be open to the assets\minecraft\textures\blocks directory within the .jar file. Paste the water_flow.png file, overwriting the version that is already there. Save the .jar file and exit your archive app.
Now fire up Minecraft, and you will have clearer water for your underwater base windows. The flowing water animation will still be there, but will just obscure your vision less.
For those using texture packs, do the same but instead edit the water_flow.png file inside the resourcepack in the directory: