NOTE! He said "at the bottom" not through the bottom.
Your lazarette is partitioned from other sections of the boat by what are called bulkheads. They are attached to the hull by glue or fiberglass tabs. Manufacturers install "limber holes" in the bulkhead to permit water to flow along the hull to the lowest area of the hull (the bilge). Then you can pump the water out of the bilge.
Boats are great collectors of contaminates. Dirt, feathers, bits of flotsam that find their way to the base of the bulkhead and tend to plug up the limber holes backing water up in various places. If you don't occassionaly clean up the spaces you will eventually find water accumulating. Then it is bucket, sponge, or hand pump needed to empty the space and clean out the limber hole.