Grow fast, hmmmmm?
Only Weeping Willow comes to mind which is not too popular.

For something long-term you could try Bald Cypress.

what about calla lillies, just read how they like water. not sure about canna lillies, but they are usually easy to grow. some irises like water too, actually grow in ditches.

With all this rain, tons of places have standing water, not just flood plains. I don't think you have to deal with it and I don't think plantings will "soak it up".

The folks buying your property need to know what they are dealing with - it is what it is.

I can't think of anything you can plant which will suck up all that water now. It would be several years before anything grew enough to remedy your situation.

Rain gardens are the current trend but they don't just happen because there's some magical list of plants that survive boggy soil.
You're moving so you're already making the mental break from your yard and its problems.
Yes, by all means, be honest with the prospective buyers but before that, try setting out some elevated planters in that boggy area and choose plants that need regular watering (medium to high moisture loving plants). Pay particular attention to the light/sun needs of these plants you choose. Consider if you have any trees that when leafed out shade this floodplain planting area.

The objective is that when your buyers look at this difficult area they will see how you have turned a negative situation into a problem solved.

Siberian Iris are what I planted in an area that had very poor drainage and flooded every time there was a downpour. In fact, that's why I planted them -- so some of the water would get soaked up. They will do well even if the area does not dry out. For me, a planting of three multiplied to many by the end of the summer. My Siberians are flooded with sunlight until noon and shaded the rest of the day. They keep their green and some varieties will flower throughout the warm seasons.

Louisianna Iris like wet areas and I tried those also, but they don't multiply as quickly as you would like.