Disaster, thy name is Neptune.
There were a lot of really good disaster movies in the seventies, and this is just a logical extension of that trend. A submarine gets trapped far beneath the waves and desperate attempts are made to rescue them. The casting is, of course, absolutely star packed, with minor characters being played by some of the best stars in the business. The main cast is just breathtaking. The movie holds its tension really well. It looks really good and is fantastically grounded. It is a child of its time and it reflects some of the values and trends of the era, but it is a great piece of cinema, and I would recommend it wholeheartedly.