For my first entry in the Boris Blogathon, I did some surfing (appropriate for the amount of Beach Party parties he did late in life) and found a few sites where you can take a peek at Mr. Karloff's final works. Such as ビキニ・ビーチ (Bikini Beach.)
Unfortunately, I can't find much information on the movie in Japanese, but here's a treat...the theme song performed live by the Yokosuka Band:
Or how about ヘブンリー・ビキニ (Heavenly Bikini-a far superior title, IMHO) from 1966 known as Ghost in the Invisible Bikini in the US. I'm unable to copy the cover, so you'll have to click the first link to see it. You'll get a brief look at Boris and a few seconds of Nancy Sinatra singing Geronimo here:
Though not a Beach Movie, one of the last things he did was a voice over for マッド・モンスター・パーティ (Mad Monster Party). It looks intriguing! Here's an unembeddable clip of It's the Mummy! It's Sick-adelic!