The word makai is used in directions in Hawaii to mean "toward the sea" or "oceanward." When someone tells you to head makai, that means to head in the direction of the water.
Makai combines the Hawaiian words ma, meaning "at, toward, beside, or on," and kai, meaning "sea." On the Hawaiian islands, the opposite direction of makai is mauka, "toward the mountains." Because the Hawaiian islands are surrounded by water and often have volcanic mountains near their centers, the sea and the mountains are useful landmarks for giving directions. So if you're told that the shaved ice stand is on the makai side of the shopping center, you should head to the side facing the water.