How to stop water seeping through concrete?

Depending on where you live, that crack may be above the frost line. Water seeps in between the discontinuous bricks, freezes, opens the crack more, and eventually cracks the whole way through. Since bulkheads are usually extended away from the house, they are colder than the rest of your basement and may freeze in cold climates. So assuming you live somewhere cold...

I would consider improving drainage around the top of the bulkhead. Slope the soil away from the house so that surface water drains away from the house before seeping into the soil, keeping the soil near the house drier. If the drainage problem isn't too bad, then you could try burying gravel so that the bottom of the gravel is below the frost line. If you are particularly enterprising, you could go so far as implementing a french drain (perforated PVC pipe + fine filter + gravel), so long as you have a place to let the french drain drain to. French drains are a really big-hammer approach though and would probable be overkill for something this small.

After dealing with any drainage issue, I would make sure that the exterior face of the concrete is continuous, especially across that line - a single continuous layer of concrete over the face of the outside may help to prevent water intrusion through that partition in the structure of the wall. After that, I would waterproof the exterior of the wall, well above and below that crack, possibly below the frost line to prevent new damage further down. This could be achieved with a waterproof membrane like blueskin or bitumen paper, or something like waterproof paint.