Marina (On Stranger Tides)

Marina is one of the beau tiful-but-deadly  Mermaids of Whitecap Bay, featured in  Pirates of the Caribbean: On Stranger Tides. In the final version of the film, she did little to distinguish herself from the other mermaids who attacked the longboat therein, however a deleted scene strongly suggests both that she knew  Jack Sparrow  before the encounter and that she has mixed-but-fairly-intense feelings for him.

Background
Marina initially appears to be simply another of the alluring, predaceous mermaids who provide great danger for the pirates who are hunting them. However, the deleted scene used in trailers or featurettes indicates that she has a quality which renders her unique; a former relationship with a human.

When Marina sees Jack Sparrow upon surfacing, the two recognize one another. The latter reacts with his typical dread at meeting one of his jilted lovers while the former delivers a sound slap across his face, a look of keen anguish clearly visible on her own. Taken at face value, this brief scene suggests that she, like Syrena, was capable of loving a human. However, Marina's affections fell upon a less-worthy man than Philip Swift, and thus her heart was broken and she became something of a tragic villainness.

Abilities
Mermaid Swimming: A mermaid's tail enables her to swim more swiftly than an equivalent human being and also to more-effectively perform underwater feats of agility. This ability was not conferred upon  Jorgelina Airaldi, however, for her tail was not swimmable like the one worn by Daryl Hannah while she was playing the role of Madison in the 1984 film Splash! Rather, the tails were computer-generated like those of the mermaids in Once Upon a Time.

Powerful Grip: Marina and her pod exhibit physical strength which is higher than that of a normal human woman. They use this superhuman strength and speed for actions as complex as using lariat cords to ensnare the throats of their victims or as simple as grabbing these victims and pulling them underwater.

Fangs: Though their torso, arms, and head appear to be those of beautiful young women, Marina and the other mermaids of Whitecap Bay have canine teeth which can extend into fangs at will. It is unknown whether these fangs are venomous or even perhaps blood-draining like those of a vampire, but they are useful when slaying prey.