The Israeli ship saw the fishing boat leaving Egyptian waters for the Palestinian fishing zone in the early morning hours of May 3, the Jerusalem Post said. When a navy officer ordered the boat to halt, it sheltered behind another fishing vessel and its crew began tossing sacks into the water.
The navy commander decided not to fire on the suspicious fishing boat because of the risk of hitting others and allowed it to slip away. A few days later a navy retrieval unit sent a robot down, found the sacks 30 meters (100 feet) below the surface and obtained a sample of the contents, which proved to be TNT.
The 13 sacks contained a total of 550 kilograms (1,200 pounds) of TNT.
Major Oren Raba, head of the underwater retrieval unit, said the explosive appeared to have been scavenged from mines.
"This attempt is significant, since the high-quality explosives discovered could have been used in devastating terror attacks against Israel," said Col. Yoram Lex of the Ashdod Naval Base.