Dead Water starts with a combat veteran, his wife, and the brother of the veteran's best friend going on a multi-day trip on the friend's fancy boat. (The best friend died in combat.)
Whew! Now, personal tension between all three occurs, of the pesky superficial kind. The characters act in one fashion and then flip suddenly. But, did something happen when our combat veteran was away?
Well, all of that doesn't matter. The plot has only minor things to do, and it's written so poorly that the scenes jump in the middle of themselves from drunk fun to caustic accusations.
And to make matters worse, there is another plot that is inane. And doesn't need any description here as it will be obvious when it first peeks its head above water. (Get it? A movie on the ocean? Water?)
Acting is fair to poor, but it may also be related to how bad the dialogue is. If you are watching this for Judd Nelson, I'd pass as he has a small role that has no depth, and is really a throw away of a role.
Dead Water is dead in the water.