Put down your goals and make notes on your progress toward those goals. Quite simply, it will make the time you spend in the water more productive. You will be more aware of what you are doing in the pool during every workout. Things that were barely on the periphery of your consiousness in the past will come sharply into focus if your goal is to gather useful information. You will find that the mere fact that you will write something down will make you more alert to it - that's half the reason you were drilled to take notes in school.
Abstract concepts become clearer.
Concepts that you have a marginal grasp on will tend to sort themselves out when you have to verbalize your thoughts. This typically ellicits questions you need further input on. Write the questions down and then make a point of cornering your coach to get the answers. Write the answers down. It is a natural fact that people learn more rapidly if the information they get is in response to questions they have have asked.