No water-borne radionuclides from Fukushima’s Dai-ichi nuclear reactors have been detected in Hawaii’s waters by scientists of the University of Hawaii, Hawaii Department of Health, or Surfrider Kauai.                              

Surface ocean cesium-137 activities near Midway (M1-M6), Guam (G1-G7), and Hawaii measured over 24 months. The coastal (Honolulu, Sans Souci beach) and offshore (Station Aloha) samples had very consistent cesium levels corresponding to pre-Fukushima activities throughout 2011, 2012, and 2013.

University of Hawaii scientists have been monitoring radionuclide levels (cesium-134 and cesium-137) around the Hawai‘i Islands following the Fukushima Dai-ichi nuclear power plant accident. Dr. Dulaiova’s findings through the end of 2013 show that ocean water around Hawaii does not yet have measurable levels of Fukushima-derived radiation. Check Dr. Dulaiova’s website for the results of water testing.
http://oos.soest.hawaii.edu/pacioos/projects/fukushima/

U.S. Scientists have put up websites trying to provide the most accurate data and interpretation of measurements of radiation in the ocean and marine life. Numerous reports posted on-line and through the social media have alarmed many people. Most of the alarm is unfounded for Hawaii and west coast of North America. Computer models of predicted tsunami wave movement have been improperly portrayed as describing the actual presence of radiation in the ocean. Here are two recommended sites that discuss movement of the radionuclides in water and animals.
http://blog.safecast.org/
http://www.ourradioactiveocean.org

Most marine life that becomes contaminated with Fukushima radiation remains near the reactor, but some species, like Bluefin tuna, are far-ranging and even migrate across the Pacific. When these animals leave the Northeast coast of Japan, some isotopes remain in their body, but others, like cesium, naturally flush out of their system. (Credit: Madigan, Baumann, and Fisher) – See more at: http://www.ourradioactiveocean.org/#sthash.aBeJhQjd.dpuf

Hawaii Department of Health has been monitoring radiation levels of Hawaii’s beaches and in marine debris that has washed up. To date no levels above those low levels emitted by Hawaii’s rocks and sand have been detected. These results are posted on the DOH website at http://health.hawaii.gov/irhb/japan2011/

Surfrider’s Kauai Chapter purchased a professional grade Geiger counter after the conference on the effects of the tsunami Surfrider put on at Kauai Community College in December, 2011. Dr. Carl Berg was trained and certified in its use by the Hawaii Department of Health. Since then measurements have been taken of marine debris including pieces of boats, nets, ropes, floats, floating docks, a fuel tank, lumber, propane tanks, and refrigerators. All measurements were equal to background levels of the nearby rocks and sand. Surfrider Kauai will continue to monitor large marine debris as it comes ashore and plans on presenting a conference on the status of radiation and marine debris from Fukishima around the time of the third anniversary of the tsunami, in March 2014. See the SOEST website for photographs of large debris from around Hawaii: http://iprc.soest.hawaii.edu/news/marine_and_tsunami_debris/sightings.php