Lobelia cardinalis (Cardinal Flower/Red Lobelia) will grow in wet ground and can cope with dappled shade.

It's a nice plant but our slugs love it.

My husband says there's a blue one, Lobelia siphilitica which could go at the edge of a pond, and it loves shade.

Unfortunate name : was once thought a cure for syphilis evidently.

Thanks for info, Yorkshire bloke trying to get a nice (wet)
garden on the sunny banks of the Clyde nr Glasgow

Good luck Jed