The Coast Guard had been monitoring the strong winds and high waves. The Coast Guard Cutter Florida was headed toward the beach to warn swimmers about the danger. They were ready to post red flags warning of a strong undercurrent. Over the summer, many swimmers had been rescued. The coastal beachfront was especially prone to a strong undercurrent because of the Gulfstream. Several guard members on the boat watched the scene unfold as the cutter headed toward shore. They saw two surfboarders heading toward a small raft with a young child inside. The raft was close to flipping over. Several guard members on the boat watched the scene unfold as they headed toward the shore.

What implicit idea is expressed in this sentence?