2.4GHz band 
Unfortunately, the 2.4GHz band does not work in water because it is the same frequency that is used in microwave ovens. They both use the resonant frequency of water molecules; water absorbs the waves and gets a little bit warmer in the process.

900MHz band
A couple of our users have had some success, though limited, in water using this band.

Running thin antenna cables to a float on the surface of a body of water to get the antenna above the water can possibly work (even at 2.4GHz).

*Make sure you are in a country where it is legal operate on the 900MHz band

Custom Systems For This Purpose
If there is time and budget, a custom IR system could be made, but the cost would be quite high and it would take several months for new engineering using currently available components.

Another possibility, also requiring custom design, would be ULF — ultra-low frequency control.  The number of channels would be very limited and responsiveness would be noticeably sluggish, but It could certainly work within the limitations of water.