This plant is growing at the water's edge in my friend's yard. She lives along a canal in North Carolina. It has narrow serrated leaves and pink flowers with five petals.
At first she thought it was a hibiscus but the leaves and buds are wrong.
Probably Scarlet Rose Mallow (Hibiscus coccineus); the description at https://floridata.com/Plants/Malvaceae/Hibiscus+coccineus/491 might be helpful.
I'm not an expert in identification, so I'm not 100% sure, but to me it does look like a type of hibiscus, Hibiscus coccineus, as Colin Beckingham suggested.
This variety of hibiscus, is also called Scarlet rosemallow, Crimson rosemallow, Wild red mallow, and Texas star hibiscus. Some call it hibiscus coccineus Walter.
In addition to its appearance, the biggest clue for me is the water's edge location where it's growing wild. The Missouri Botanical Garden calls it a swamp hibiscus, because it grows natively in marshes and swamps in Alabama, Georgia and Florida.
Wildflower.org also mentions states where it's common, and North Carolina is on that list.
It's a perennial in zones 5 or above, making it a good choice for wildflower gardens, or anyplace you don't want to worry about replanting.
If you want to grow one and have a pond or other water source, that's the best place to put it. However, it's happy in a garden too, as long as the soil remains moist, and it gets either full sun or part shade. Note that it doesn't flower as well in the shade. When planning your garden, leave it plenty of room, as the average full size is up to 3-6 feet high and 2-3 feet tall.
Each flower doesn't last very long, but it continues to bloom profusely from late spring into September, in zones 5-9, which includes North Carolina.
A unique feature of this plant is that it lends support to bees in general, and especially the Ptilothrix bombiformis. It also attracts butterflies.