The sequel to Deep Sea Monster Reigo is now in trailer form!
Deep Sea Monster Raiga trailer
This one is set 60 years after the original, in modern-day Tokyo. Global warming causes the southern polar ice cap to gradually melt, disrupting the ecosystem and luring ancient sea monsters to Japan. Eventually an enormous sea beast called Raiga enters Asakusa via the Sumida River and begins wreaking havoc on the buildings there.
Thanks to Avery for the link!