NASA identifies 17 exoplanets with possible subsurface oceans 

 Internal heating may be able to keep water in liquid form within these exoplanets. 

https://cdn.mos.cms.futurecdn.net/w9o5cE3Sts4zTWawuEucB9.jpg

https://www.space.com/nasa-17-exoplanets-liquid-oceans-beneath-surface