Roger Corman love (d) to buy foreign films, chop them up and add new footage - he did it with Soviet sci fi in the 60s and here he raids Japanese disaster movies. The original was called Submersion of Japan and apparently it's not bad - the American version isn't that great. The human drama has been truncated meaning there's few characters you can emphatise with and dramatic situations feels undercooked (eg one minute they're worried about disaster then, bang, disaster has hit).
Lorne Greene pops in as the US ambassador and there's some interesting stuff with what to do with all this refugees. Australians will enjoy a scene with an Australian ambassador. The special effects are well done. But as a drama it's a let down.