I know it's a big body of water and it will disperse eventually, but what about the safety of our diving in those waters nearby? We were planning a dive trip to the Philippines
Fukushima is in Japan, not in the Philippines.
And it's a power plant, not the Amazon river. What little pollution there is, strong even, will fade in the ocean. No big white cloud coming your way. The radiation levels are now 100 000 (?) fold. They used to be around ... 0 ? ... before. The situation is bad of course, locally, nationally even, but it's a Japanese issue.
Of course a city or two were also wiped out to the sea, but that's minor.
There's a small leak in a power plant.
Just don't swim in Fukushima without a drysuit and full face mask. Alpha and beta radiation will stop at your clothing/skin surface unless you drink the water. It's a bit like sunbathing in very strong sun light. You'll get burnt. A little doesn't harm you, but too much on unprotected skin causes skin cancer. That's the reason for the white protection suits. It's just "shade". That's also the reason why drinking water is not recommended for small children. One gets slight amounts of sun bathing inside oneself, and that is unhealthy. But then again... amounts are important. And children may be more sensitive. You wouldn't drink water from the reactor, but you could drink just slightly radiating water. Just like you can eat a bit of salt, but a spoonfull or two might kill you.
Gamma radiation penetrates deeper, but enough water stops it too. It fades out like a flashlights beam. It's even the same thing, just invisible (like UV or heat radiation or radio) and plenty more powerfull.
And this radioactive iodine that causes the trouble halves in amount pretty quickly.
I would guess that getting drunk once makes more destruction in your body.
Burnt fat in food causes cancer. And sun bathing does too.
So avoid sunbathing, fast food and alcoholic beverages and you'll be fine.
ps. your sandwitch contains a bit of radioactive carbon-14
