plants for wet soil

[OliveOil]

My parents have just moved and whilst their house is lovely and they have their own jetty at the bottom of the garden, I have noticed that the top end of the garden is water logged and very spongy to walk on.

Can anyone recommend any plants that love water  - other than pond plants lol.  I'm sure this water will drain off in summer but for much of the year it will be wet.

[OliveOil]

[ACE]

Day lillys,  flag iris, most iris siberica and crocosmia will put up with everything