If you have 2 transom mount transducers with 20 degree cone,and if you mount them 4 feet apart, you can probably run safely in water up to 5 feet deep without crosstalk.

However, if one is 50khz, and the other is 200khz, you might get by with it. This would depend on the tx power of the units. Remember, 200khz is the 4th fundamental frequency of 50 khz. Power can be damning.

I could be wrong.

Tom