Help me solve the message!

When I and my family were at a little island with our boat this summer I found a bottle post!! =D It was in a bottle of real glas, but the cork was broken, so there was water in the bottle.

When we opened it this was what we found.

 

I have no idea what it means!! Is it Japanese? Chinese? Please help me if you know, because I realy want to know!! ^^

Done