We have an area of the backyard that we call 'the wet corner'. Our property and two neighbouring ones drain into that area, so in spring (i.e. now!) it is a bog. It eventually dries out in summer but you can't walk on it at this time of year and any planting hole immediately fills up with water, although there is rarely standing water there. While not formally a 'rain garden', that area is planted with things that like - or tolerate - the conditions (it's shady too...) There are a couple of other places that are seasonally wet and I treat them the same way. Luckily none of them are areas where I would want to have a patio or seating or other functional hardscape or structures. If that is the case for you, planting is certainly the easiest option, but if the wet interferes with use, a drainage solution would be required.

Thank you! I was hoping to hear this answer. I am planning to select plants that tolerate these conditions and hopefully it would work. The place is shady too.

You said it's "always" wet and soggy - is that year 'round? I have an area that has standing water in the spring, but can also be quite dry in the summer. Some plants will tolerate one but not the other.

I've had great luck with chelone lyoni in that spot. The area is shady but not deep shade.