This focuses on mermaids appearing in full length (60 min+) cinematic features (this definition gets fuzzier the more digital everything becomes, but I trust that the members of this forum understand).
Currently making the independent film circuit (late 2015/early 2016)--and even winning some prizes!--is a Polish film, Corki Dancingu (English title, The Lure) directed by Agnieszka Smoczyńska. The overall plot: Two mermaids come ashore to become part of a band and the growing 1980's Polish dancehall lifestyle. Ultimately, they would like to move to America! However, they compete for the love of a man and against their natural instinct of eating human hearts!
Later this month (Feb 2016), a third Chinese mermaid film is set to premier: Goodbye/To See a Mermaid 《再见美人鱼》(The title apparently translates either way.) There are already trailers (including one dubbed in English!) and a music video online.
Stephen Chow (a Chinese actor and film director, perhaps best known in the US for collaborating on the martial arts/special effects/comedy film Shaolin Soccer from a couple decades back) is scheduled to release Mei Ren Yu (美人鱼), a modern day comedy take on The Little Mermaid. It is scheduled for release in Chinese theaters February 2016.
The notional story: A marine biologist encounters a mermaid; she comes ashore to become better acquainted with him.
"Xiaohua Xiaohua 3 of the drive to Mermaid" 《校花驾到3之人鱼校花》 is a mermaid-centric film that looks like it will premier early this year (2016). A promotional poster of the titular mermaid (enjoying an obligatory bubble bath in a tub) has been posted in the Seatails Facebook page.
A late 2014 direct-to-video CG movie, "Monster High: Freaky Fusion" features a ghostly mermaid.
The story in short: Most "normal" monsters go to high school, and a quartet of new students have transferred in. However, as they are monster fusions--i.e., mixed breeds--they do not gain a lot of acceptance at first from our protagonists. [That attitude is likely to change by the end.]
A late 2014 entry into the ongoing string of direct-to-video Barbie movies is "Barbie and the Secret Door." A spoiled young princess is stealing all the magic from the world, leaving one mermaid stuck in human form. Said mermaid joins Barbie in a quest to set things right.
[There are a couple other very minor mermaid characters, part of a pod of mermaids who have yet to lose their tails.]
Pacarku Putri Duyung is an Indonesian TV movie that aired in early October 2013. The basic premise: Set in a modern-day town, a mermaid rescues a male student from drowning . . . but in return (plus some bribery), she asks him to help her find an elderly mermaid [presumably her Grandmother] who disappeared somewhere on land. The student provides her a cover identity, a place to stay and some clothes. Meanwhile, the grandma mermaid is being kept caged up by some nefarious thieves, who want her for the tears she cries. [Said tears become pearls.]
Ngye Tshomen (My Mermaid), directed by Wangchuk Talop, was allegedly a "blockbuster" romance film in Bhutan last year (2012). The actress Tandin Bidha had the titlular role.
I have not found too much on the film itself besides a few photos on Google image search and a few minutes of clip video on Youtube. Still, it appears to be very much the Bollywood style of film (i.e., lots of dance numbers and singing). The mermaid and costume looks decent enough, but anything beyond basic underwater photography appears to be CG.