The water is just the run-off from the water they've been spraying on it for 2 weeks, and they only started monitoring the sea around the area a few hundred feet out at the weekend. So it's probably been like that for 2 weeks, and it soon gets watered down.
The plutonium is just from a partial meltdown of exposed fuel rods, and they have it under control as the temperature of the rods is now manageable. Plutonium is not that good in soil, but it's only small amounts. It would be better if it was uranium as it's half-life is vastly smaller.
