Is this correct?

Google translator tells me that "sea monster" translates as 海の怪獣 (in kanji). Is this correct? Thanks!

Yes.
Or 海の怪物.

怪獣(Kaiju) looks like dinosaurs such as Godzilla.
怪獣: http://goo.gl/AUSnc

怪物(Kaibutsu) is something mysterious/powerful and maybe not so huge.
And you can use 怪物 for a person, superstar, Mr.Big, GodFather and so on.
怪物: http://goo.gl/tWnDQ
(Some images are a bit grotesque!)

Unless you particularly mean the following.
sea giant on folklore : 海坊主(Umi-Bouzu)
http://goo.gl/5MoER
silver chimaera : 銀鮫(Ginzame)
http://goo.gl/TlC9O

Thank you, ajapaneseboy!

This was very helpful and informative. I love the Umi-Bouzou character, but my 'sea monster' is of the general kind :-)

The translation will be portrayed on my bike (frame re-spray), which I will be taking with me to (and ride across) Japan next year.

Thanks again.

I'd like to see that respray. Best of luck for your trip. Have you ridden in Japan before? If not it can be fabulous but route planning is very important to avoid busy roads with many large trucks & tunnels, oh and absurdly steep hills :)

I'd like to see that respray.

I will dig up this thread and update it with links to pictures, when it's all done. Which won't be anytime soon, since I still have to buy some parts, complete the build, take it apart, and send the frame for the respray and some minor adjustments to a specialized shop. The frame is On-One Inbred 29er. You may be familiar with the brand ;-)

Best of luck for your trip. Have you ridden in Japan before? If not it can be fabulous but route planning is very important to avoid busy roads with many large trucks & tunnels, oh and absurdly steep hills :)

Thank you, Stan. No, this will be my first time in Japan. I know, the planning stage has shown to be much more laborious than I had thought so. I am piecing the route together from multiple sources and it takes time, simply because there is so much to see and so many options. I will present it in parts (the length of Japan plus some would be too much info for one thread) in the travel section as soon as I have it together. Mountainous and hilly indeed! The granny gear will get a shot at glory :-)