As a former US Marine who is quite familiar with the effects of artillery, I must point out that a careful viewing of the media video of the after effects of the Gaza explosion showed NO artillery round craters.

Israel's IDF uses 155 mm artillery shells. These are quite powerful and invariably leave a crater, some as deep as four feet in soft soil like sand. Virtually none were visible in the film. Particularly in the area immediately adjacent to the family's alleged picnic site.

There is something very wrong in this entire story about that explosion. Unfortunately, the Palestinians have already reaped the benefit from a world media all too eager to blame Israel.

Michael Allen    6 12 06

UPDATE:

Michael Allen's insight is confirmed by an Israel Defense Forces report, just released and published in the Jerusalem Post:

The IDF probe investigating the deaths of seven Palestinian civilians, caused by an explosion on a beach in Gaza on Friday evening, concluded that chances were slim that the accident was caused by IDF shelling.

According to Channel 2, the findings, expected to be formally released on Tuesday, showed an inconsistency between the shrapnel found in the body of one of the wounded babies and the metal used in IDF artillery.

Moreover, the investigation noted the absence of a large enough crater at the site of the explosion, as would be expected if an IDF shell had landed there.

The third observation casting doubt on the possibility of IDF shelling was the gap between the time when the army shot the artillery and when the commotion on the beach began. According to the probe's findings, several minutes past after the shelling, before the Palestinians on the beach reacted.

On Saturday evening Gaza Division Commander Brig.—Gen. Aviv Kochavi insisted that the sites that were shelled by the IDF were the places from where Kassam rockets were launched. He noted those places were frequently targeted by the IDF, and were known to be dangerous places.

The leading theory currently entertained, suggested that an explosive charge, buried by Palestinians on the Gaza beach to prevent Israeli infiltration, was behind the explosion.