French nuclear analysts have used radiation numbers, publicly release by Japanese officials, to determine how bad the contamination is in the Pacific Ocean.

The Institute for Radiological Protection and Nuclear Safety determined that with the current level of contamination (that is the contamination that has already happened) fish and seaweed will need constant monitoring. Also, they said the high levels of radioactive contamination, recently spilled by reactor 2, will spread through out the Pacific Ocean in three months.

They pointed out that some radiation will float with the ocean currents, while other isotopes will sink to the ocean floor.  The ocean does not affect isotope half life, so cesium-137 still has a half life of 30 years in water.  Cesium-137 is in the ocean.

This does not assume any further contamination, so expect it to get worse.