I can surf on mountains over water

Dear community,

I have a little problem and need you help.
I created a new map and put water on layer 1.
I've tried terrain tag 5 and 7.

If I am on a mountain or in the sand and press the a-button it will ask me to surf.
How can I fix it?
Thanks a lot!

Probably there is a water tile underneath the mountain. You have to go to Layer1 and check my hypotesis: if you find it, delete it.