ive got a riverfront property im trying to manage, and ive got several options of herbicde that were left to me by my dad. Roundup, grazon P+D, remedy, and surmount. Is there one that is better for clearing this shoreline of aquatic weeds than others?

Any of those labeled for aquatic use?

Cattails are notoriously hard to kill with herbicides.

Aquaneat is what you probably want.

I've never had any luck spraying established cattails.Glyphosate ( Roundup) would be my first choice on young, rapidly growing plants. Good luck.

Envisioning a riverbank being a high profile area in public view -A word of caution. I don't think any of the chemicals mentioned are labeled for aquatic or riparian use. I would double check the labels ( the labels are the law).
Also Surmount and Grazon use requires a private applicators license issued by the Texas Department of Agriculture.
So if you are "caught" you are technically breaking the law and could be significantly fined.

It's more important for water quality and potential fish health.

Lots of water will help dilute chemicals but please don't just go spray a **** load of roundup on the cattails. You're gonna end up killing a lot of fingerling and fry.

I'd suggest cutting the cattails as low as you can and either spray them as soon as they start regrowing with an appropriate herbicide or give them a few weeks of growth and hand apply (wipe) with herbicide.

Roundup, surfactant, and hot weather will nuke mature cattails. Really doesn't need to be a heavy soaking.

I can't comment on fish. I use it in a seasonal wetland with no fish or runoff.

I bought some Rodeo weed killer and it knocked the cattails out in our pond.

Whoop Delecto said:

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I eradicated mature cattails along several thousand feet of shoreline using a mix of Rodeo with a surfactant (AquaKing). Worked great and they never returned.

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I was trying to remember "Rodeo" yesterday. It amounts to Roundup with an aquatic label, as I recall, and a good surfactant is essential on cattails and such (their leaves really tend to repel spray solutions without it).

I have used a tank mix of glyphosate and imazypyr with success in June.