When you are scuba diving in the sea, strong currents might come along and sweep you away. You need to have the presence of mind to locate where you are and which way is up, and learn not to panic and use up all your air. Similarly, in inquiry, in the inner ocean, you might easily be distracted or swept away by strong feelings, whether pleasant or unpleasant, or by the endless chatter of your mind or the sensations of your experience. So it is important to learn how to maintain a certain focus and presence of mind. You need an anchor in the midst of the flow so you do not get swept away. This means developing your powers of concentration, and that is done using meditation.

Concentration meditation is a bit like training for scuba diving by lowering yourself into the water over a big round rock, and then keeping one hand on the rock and maintaining your position above it. There is not a whole lot that you have to deal with in terms of navigating and looking around. Your job is just to stay above the rock, to practise keeping yourself in one spot and breathing in a relaxed way while you are in the water. Fish might swim by, the waters may be surging or calm – it does not matter. The water conditions do not change your job, which is simply to keep next to the rock whatever else happens to be going on.

From Diving in the Inner Ocean, chapter four

Moving to the inner ocean, the focus that you will use – the rock – is the immediate sensation of your lower belly. It is centred on a spot a few inches down from your belly button, and about an inch inside.

In the meditation, your job is to attend to the sensations of this part of your body, simply staying in touch with them as continuously as you can.

Your attention may get pulled into something you are thinking about or feeling, or it might be drawn to noises or distractions around you. These are like the currents or fish in the water. If and when you notice that happen, simply bring your attention back to sensing your belly, just like swimming back to the rock.

You are not trying to stop the thoughts, feelings, or other sensations at all. You are not trying to calm the sea or get rid of the fish. You are practicing not letting them take you away from your rock and coming back to it whenever you do get pulled away. You are staying in touch with the sensations of the breath in your belly, whatever else may be going on.

From Diving in the Inner Ocean, chapter four