This is because few have ever seen a male of the species, since the Children only tend to have 2-3 of them for a colony of about 40, and since they're smaller and frailer than the females. Whereas female Reedfolk are about the size and shape of a petite human woman, the males are generally built as a skiny, short, halfling man. Mass and strength are roughly comparable. Regardless of gender they have pale green or grey skin, are excellent swimmers and have the capacity to stay underwater for long durations. The Children of the Reed in general can be regarded as pleasant looking, if one can disregard the fact that there's aquatic and semi-aquatic invertebrates and plants sometimes living in their hair.
They're kinda sneaky (from here)
Since the Children have few males and they tend to be weaker, they are usually left at the semi-submerged woven reed nests that the Reedfolk construct on the lakes they inhabit, looking after the young and making and repairing the few tools and weapons they use.
Like this, but on a lake and there's more of it under water (from here)
The Children tend not too have much in the sense of possessions. Clothing is unusual unless there's non-hostile contact with races that tend to view clothing as preferable, but even then clothes will only be worn for some interactions with outsiders. Decorative trinkets of bone or shells are common, however. Their tools and weapons are mostly made of bone and wood. Reedfolk pretty much distrust metal and will reject metal tools and weapons if offered. Even stone is considered as somewhat suspect, although some bolder warriors will opt for a stone knife or spearhead instead of the more usual bone.
They're still pretty dang sharp even if they're brittle (from here)
If you visit a (demi)human village that is near a colony of Reedfolk, there's a possibility that you'll hear rumors of the Daughters of the Reed kidnapping people, especially children. Some might even accuse them of eating the kidnapping victims. These rumors are somewhat exagerated but the Reedfolk do occasionally steal unattended human or demihuman babies. They do not, however, eat them. Truth is that the Children's seeresses know how to prepare a potion which if fed to the infant with appropriate rituals will transform it into a Reedperson with a 25% chance. If that doesn't happen, the baby will almost certainly die, unless healed by magic - in which case it once again has a 25% chance to turn into one of the Children. Reedfolk thus produced do not differ in any way from the regular ones, and there's a possibility that Reedfolk in general are an ancient magic experiment turned loose.
She's gonna turn your kids into more of hers (from here)
Using in a game
The females should be treated as humans with water breathing and the males as halflings with water breathing. Males are non-combatants. Females will mostly fight with bone spears and knives (should break easily, say 1-4 out of 6, if used against someone with metal armor... although metal armor against someone who can just pull you underwater would be a dangerous idea). There's a 25% chance that one per 20 Reedfolk will be a shaman/seeress (roughly equivalent to lvl. 1 Magic User or whatever you like).