Zak Waters (born January 22) is an American musician, singer-songwriter, DJ, and record producer from Los Angeles, California, also known as Pretty Sister.

Waters began his music career forming the band Blueskyreality. After the group disbanded, Waters started his solo music career, releasing his debut extended play (EP), New Normal (2011). He featured on Madeon's 2012 multi-platinum single "The City", to positive acclaim, charting at No. 20 on the US Hot Dance Club Songs chart and No. 16 on the UK Dance Chart. He released his debut studio album, Lip Service, on September 9, 2013. The following year, he released his second EP, Now // Later on June 17 on Rostrum Records and his studio cover of Ginuwine's "Pony" to critical acclaim. He collaborated on Adventure Club's gold-certified single "Fade", which further prompted Waters to international recognition. He also collaborated on other popular singles including Adventure Club and David Solano's "Unleash (Life In Color 2014)" and Alex Gaudino and Manufactured Superstars's 2015 single "Lights Go Out".

As Pretty Sister, he has released three extended plays; Z Funk Era, Vol. 1 (2018), Poolside Vibe (2019), and 20 (2020). He has featured on other artists' singles including Nause's platinum-selling single "Dynamite" and Keljet's "Love At First Site". He featured on LDN Noise's "Tears", which was released in August 2016. He has collaborated and produced for various other music artists including Betty Who, Breathe Carolina, Nathan Sykes, Superfruit, and JoJo, among others.