Can a body exceed 3/4 the speed of light in water.
You might be interested in http://en.wikipedia.org/wiki/Cherenkov_radiation
Weakly interacting particles, with no charge, like the neutrinos, will (almost) not be affected by water or any other environment.
Such particles will maintain their existing velocity, close to the speed of light in the neutrinos case.
then will a phenomenon like sonic boom would occur?
Cherenkov effect is analogous to sonic boom for sound.
Yes, there would be Cherenkov radiation radiating at a certain angle to the trajectory of the particle.
Separate names with a comma.