Well, a trawler can tell you, when she puts her net over the side and drags for 20 minutes and comes up empty, that she knows she's in the dead zone.
Baik, kapal pemukat dapat memberitahu Anda, saat jaringnya didorong ke laut dan diseret selama 20 menit dan datang tanpa isi, bahwa ia tahu ia di zona mati.