Rip currents are a relatively strong, narrow current flowing outward from the beach through the surf zone and presenting a hazard to swimmers. Signs of a rip are rough, erratic, or choppy surf, where otherwise it is calm; foam or debris that can be seen traveling outward; a discoloration to the water as a result of sand and debris, looking muddy or dirty (Figures 5 & 6). The most dangerous times for rip currents are the three hours preceding high tide and even more so the three hours directly after high tide. Rip currents cause about 80% of needed rescues, because swimmers will be unaware of how far out they are, and use too much energy to attempt to swim back. Figure 7 shows how a swimmer can self-rescue from a rip.