Well how big is the pond? Are we talking a 1 acre dug out pond? Or a few hundred gallons?

Just gently grab a few pads and try and lift the entire plant out. It's kind of like a thin pineapple looking thing.

If you take that out, no more pads. Or just cut it in half, and throw it back in. Throw the other half in your compost pile or trash.

I wouldn't try to 'kill' it with anything. Just take it out manually.

You are going to have to physically pull it out, not try to poison it.