You are at stop #49 on the Belmar Treasure Trail, near the end of the Belmar boardwalk, although Belmar continues until the brick arches, which mark the boundary of our neighbor, Spring Lake. In the summer, the 20th Avenue beach is a haven for ocean kayakers and you’ll see some impressive wave-riding feats. This is also a good spot to mention the rock-like piles seen along the oceanfront that most people call jetties. Jetties, however, are the rock barriers found on the sides of inlets, like those along Shark River Inlet between Belmar and Avon. The other rock formations you see along the oceanfront are actually called “groins.” These groins are manmade formations originally built like solid rock walls jutting into the ocean to protect the beach from erosion. But in 1990, following a massive beach replenishment, the groins were notched near shore ...