In underwater environment, Why acoustic underwater communications are still famous more than magnetic induction communication however in magnetic induction underwater communication, higher data rate is offered, shorter propagation delay and highly environment-independent channel behavior? In other words, what are they disadvantages of using magnetic induction communications in underwater environment?
Actually, magnetic induction is a current research topic for underwater communications, see http://bwn.ece.gatech.edu/papers/2015/j14.pdf. Also, this paper includes a nice comparison of underwater communication strategies, including electromagnetic waves, acoustical communication, and optical communication.
One major disadvantage of magnetic induction is the short communication range below 100 meters. Acoustical communication has a range that is much larger in the region of kilometers.