For a design project at school I need a way to track a short distance underwater (swimming pool). I have looked into programming an accelerometer to measure the distance traveled, but that is not accurate enough for the purpose I would like to use it for. IR and GPS are both not suitable to use for underwater purposes either because of accuracy and interference issues. I was thinking about ultrasonic waves but this seems to be an expensive solution. Any suggestion is welcome!
The aim of the project is help visually impaired/blind swimmers. I need to track the distance between them, while swimming, and the end of the swimming pool in order to advice them when to turn because this is a big trouble for them. So, How can I measure the distance between two points in the water, one moving and one stationary, in order to sent a signal when a certain distance is achieved?