Melissa6 wrote in post #17250616
When would you suggest I use the lens hood? For wider shots that include the sky or beach? Or for the majority of the time? (I realize that it's purpose is to block some of the light.)
Its purpose is to block light that hits the lens at a glancing angle steep enough not to be part of the image, but which could be bounced around inside the lens causing unwanted internal reflections ("flare"). The correct hood will never affect your exposure.
I use them all or most of the time on most of my lenses. On some lenses I don't use a hood at all. It depends a bit on the lens - some have a deep bezel which performs some of the same task. And, with zooms, the kind of hood Canon supplies is only completely effective at the widest setting; otherwise, it would need to be adjustable.
Also, I realize that the filter would be for photographing the water... would a lens hood be used at the same time as the filter?
I tend not to. Usually you have to remove the hood to fit the filter. With a polarizing filter, you have to turn it to the correct angle, and that's hard to do with the hood on. Once I've adjusted the angle, I only put the hood back on if there's a big risk of flare, which depends on where the sun is.
amfoto1 wrote in post #17250516
...a quality filter such as the B+W Kaësemann MRC costs close to $100 in that size, but is worth it for the best image quality, IMO
The B+W Käsemanns are very nice, and I have two of them, but my 67mm is the cheaper non-Käsemann B+W. The Käsemann just has better weather sealing and should last longer in rough conditions (it's someone's name, "Cheeseman" in English, not some optical effect). I doubt your lenses are weather-sealed, so I don't think you need to spend that much extra on a filter. I can see no image quality difference between the Käsemann and non-Käsemann B+W filters, but a difference between B+W and some lesser brands.