I bought one a month back and it said the same message.
I took it back to the store the next day and asked?
Of course the answer was "oh yeah it is submersible", But I I traded it out for one that did not have that message on it!
I asked the shop employee if he was going to enjoy working for me when my pregnant wife was electrocuted when she went to check on why all the fish were dead. Because, I would certainly sue the owner for the store and his car and his fish tanks and his house and I'd probably take all the dog doo doo in the back yard too!