In the past, Punalu'u has suffered severe erosion by the ocean. In 1868, a huge tsunami that was caused by an earthquake struck the area. Waves as high as the coconut trees suddenly rolled in and leveled every shoreline village from South Point to Kumukahi. The residents later rebuilt the village at Punalu'u and in the 1880s, a pier was built to move the harvested sugar cane from the surrounding plantations via interisland steamships. But when more roads were built and automobiles were available to transport goods, the Punalu'u shipping point was abandoned and Hilo became the Big Island's main port. The area was hit by two other tsunamis in 1960 and 1975.
The best part to enter the ocean at Punalu'u is at the northeastern end of the beach because there are fewer lava rocks at the water's edge. There is also a small boat ramp in this area, next to the ruins of the old pier. Swimmers should keep in mind that there is a strong rip current that runs out the boat channel into the open ocean. So it is best to stay away from the northeastern point of the bay.