Positioning two devices through an obstacle on an Arduino?

Question

Arduino

There are two moving objects. One is under the ice (lower), and the other is on the surface (upper, man). How to transfer the position of an object that is under the ice to an object that is on the surface?
The lower object moves with the float leaning back against the ice i.e. doesn't sink. A person needs to know where his device is located.
Through ice 1-1.3 meters thick, gps probably does not catch.