KMC Forums - What is this film?

For ages I have been trying to find out what this 70s horror film was called. Saw it as a child. It is about a haunted house or mansion a group of kids/couples enters said house and the house is like alive and once inside the couples cant get out they try and the house starts to kill them only thing i remember is someone gets out and is on the front lawn and the lawn opens up and swallows him up and in another scene someone is swimming in the pool and like an invisble barrier prevents the swimmer from emerging from the water and he drowns and in the last thing i remember is someone takes a electric saw and trys to cut thru the front door or window shutters and he saws through his hand ?? I think at the end they get to a red basement and a man is sitting there and he is the devil?? if anyone can help me name this movie pls .