A sirine appears to be a normal human woman in most respects, although its skin often has a noticeable yellow or green tinge. The hair can be any normal, human hair color, or it can be lustrous silver or dark green. A sirine wears only lightweight clothing while on land and often nothing at all while in the water. The typical sirine carries a short sword or dagger at all times.

Sirenes are playful, gregarious creatures that love to sing, swim, dance, and laugh. They frequently draw strangers into their games and parties, but they rarely grant such visitors more than a few hours of their time.   Although sirines are always happy to have fun with strangers, they are extremely reclusive about their communities. They take care to seek camaraderie only when away from their homes, and then only for a short while. Any creature that follows a sirine home, or stumbles upon that location accidentally, is likely to come under attack.   After a few hours, most sirines have had enough of the companionship of other creatures, so they slip away, usually by diving underwater. For a stranger, earning the trust of a sirine is nearly impossible. These creatures trust no one except other sirenes, though in times of need they do accept any offered aid. Such assistance does not earn the giver any more of a sirine's company than would otherwise have been bestowed, however, nor does the creature feel obligated to reward its benefactor in any way. Occasionally a sirine bestows a gift, usually a small gem, seashell, or other trinket, on an admirer who has been particularly charming company.