A young and modern couple who go to France to explore an underwater house and share their findings on social media undergoes a serious change of plans when the couple enters the interior of a strange house located at the bottom of a lake and their presence awakens a dark spirit that haunts the house.
 
The original story idea and the fact the film isn't terribly long makes this one worth watching.  
 
FUN FACT:  The Montagnac family motto is the French translation of a famous H.P. Lovecraft's quote: "That is not dead which can eternal lie, and with strange aeons, even death may die."