Most triathletes struggle with swimming. At the pointy end of races we have started to see swimming times come down to what they used to be for international distance races. Many of us are trying to balance athletic performance (and enjoyment) with having families who recognize us and managing some kind of career. The training tool you need is the one that may just take you to the next level: the Vasa Ergometer.
Basically, you lie on your stomach on an elevated padded platform that moves up and down on a rail. In each hand you hold a swim paddle that is attached to a resistance unit via a cable. As you "swim", the Vasa provides resistance and ideally the platform should stay stationary.
Vasa can also help improve your swim technique while not putting demands on your mind - like breathing - as you get coaching or at the very least, as in my basement, watch your form in a $3 mirror from Target. The Vasa Ergometer doesn't require all of the motions of actual in-water swimming. It should be considered a supplement to your pool workouts.
This isn't to say that you cannot TRY to replace all your swims with Vasa. I haven't swam a masters practice since late fall of 2004. While I was able to be MOP with this training, I wouldn't recommend it if "qualify" is anywhere in your vocabulary. If you do swim regularly and "qualify" is in your speech pattern, then Vasa can take you to the next level.
We train with power on the bike. Training with power on the run is coming. Vasa Ergometer brings training with power to your swim.