The dilution of the radioactive content by the ocean is probably high. Overall the risk is low for significant contamination due to the overall ocean volume.

The issues are so-called hot-spots which cause certain fish to be extremely radioactive and streams causing concentrations of radioactive materials highly contaminating only certain regions and fish.

That being said, there are so many pollutants in the oceans that I'm confused why people are not more outraged about ocean pollution.

Vice Documentary about garbage streams. e.g. https://www.youtube.com/watch?v=D41rO7mL6zM

Finally, its certainly not acceptable to have on-going ocean pollution, which is probably happening in Fukushima Daiichi.