Radio communication is not a suitable technology for underwater communication due to the high absorption of radio waves in water.

The range of underwater acoustic communication is primarily affected by the frequency of the acoustic signal, with lower frequencies having a longer range.

Optical communication offers high bandwidth, allowing for the transmission of large amounts of data.

The main challenge associated with underwater optical communication is the absorption of light in water, which limits the range and reliability of the communication link.

MIMO (Multiple-Input Multiple-Output) is a type of underwater acoustic communication system that uses multiple transmitters and receivers to improve communication performance by exploiting spatial diversity.

Spread spectrum techniques are used in underwater acoustic communication to reduce the power spectral density of the signal, making it less susceptible to interference.

Wired communication is a type of underwater communication system that uses a cable to transmit data.

Wired communication offers low latency, making it suitable for applications that require real-time data transmission.

Wired communication for underwater applications faces challenges such as high cost of deployment, susceptibility to damage, and limited mobility.

The capacity of an underwater optical communication link is primarily affected by the wavelength of the optical signal, with shorter wavelengths offering higher capacity.

Optical communication is a type of underwater communication system that uses a laser to transmit data.

Lasers offer high bandwidth, allowing for the transmission of large amounts of data.

The main challenge associated with using a laser for underwater optical communication is the absorption of light in water, which limits the range and reliability of the communication link.

Adaptive modulation and coding is used in underwater acoustic communication to improve the spectral efficiency of the communication link by adapting the modulation and coding schemes to the current channel conditions.

Buoy-based communication is a type of underwater communication system that uses a buoy to relay data between underwater nodes and a surface station.