OK. But the nuclear blasts were much closer to the coast, and there were many on land.
BTW, by 'many', do you mean 5, dozens, hundreds ?
Those nuclear blasts resulted in the US paying “downwinders” for illnesses and loss of livestock decades later. The strategy for the US and other nuclear govs is to deny while the litigants or people who would hold them accountable are still living. But eventually, the truth comes out and it’s counted as a “success” because few are around to collect. On one of these threads, a spouse of a “Downwinder” (people downwind of nuclear testing in US and she was the only surviving member of her highschool class - all others had died. He chimed in to say that nuclear testing back then had real effects that the US gov denied. SO I went looking for information and found financial settlements etc. and sad tales of entire herds of cattle down from radiation and the US wouldn’t allow local veterinarians to testify at trials - only gov veterinarians who said nothing was wrong - just a herd of cattle dead....move along.
Justa-Hairy-Ape went back and read up on nuclear blasts in the US and offshore and did the calculations and to get an equivalent “dose” of radioactive waste from those blasts to some level of Fukushima, you’d have to detonate 40 blasts a day. And that was a year or two ago - the radioactive waste load Fukushima has been dispensing into the environment has been continuous during that time.
Re your question about number of nuclear blasts, “The United States conducted 1,032 nuclear tests between 1945 and 1992: at the Nevada Test Site, at sites in the Pacific Ocean, in Amchitka Island of the Alaska Peninsula, Colorado, Mississippi, and New Mexico.”
http://www.ctbto.org/nuclear-testing/the-effects-of-nuclear-testing/the-united-states-nuclear-testing-programme/