1. Dissolve a long-lasting dark dye in seawater, let it enter the bottomless pit, and check whether there is marked seawater in the surrounding sea area.
2. Put a small plastic particle with a density similar to that of water into a bottomless pit and search for the small particles in waters around the world.
1. They dissolved a long-lasting dark dye in seawater, let it enter the bottomless pit, and checked whether there was dyed seawater in the nearby waters, but they did not find that seawater;
2. They put a small plastic particle with a density similar to that of water into the seawater flowing into the bottomless pit, and searched for these particles in various waters, but they did not find the particles after searching for a long time.