Submarine cables are usually one of the main methods used to transmit telecommunication signals and Internet data. They are installed at the bottom of the sea to connect different geographical locations, making global communication networks more stable and reliable. Submarine cables have some unique advantages and disadvantages, each of which is described below.

Advantages:

1. Fast Transmission Speed: Submarine cables typically transmit faster than satellite communications. This is because the transmission path of submarine cables is more direct and the signal transmission is not affected by factors such as atmospheric interference, which can provide more stable and high-speed communication services.

2. High network stability: Submarine cables are subject to relatively little external interference and can provide a more stable and reliable network connection. In contrast, satellite communications are more susceptible to weather and other external environmental influences, and are prone to signal interruption and other problems.

3. Large bandwidth: Submarine cables usually have a larger transmission bandwidth than other communication methods, which can support more data transmission and higher-quality audio and video calls, among other services. This is why submarine cables have become one of the main transmission methods for the global Internet.

4. High security: Submarine cables are more secure and more difficult to hack and listen to than wireless communications and other methods. This is one of the reasons why many governments and businesses choose to use submarine cables for sensitive data transmission.

5. Low cost: Although submarine cables are expensive to install, they are relatively inexpensive to maintain and operate. The overall cost of submarine cables is more cost-effective than, for example, satellite communications.

Disadvantages:

1. Difficult to install: the installation of submarine cables relies on specialized techniques and equipment and is often difficult to install as it needs to be carried out in a marine environment. Certain geographic locations, such as the deep sea, are more costly and time-consuming to install submarine cables.

2. High maintenance costs: Once a submarine cable fails or is damaged, repair and maintenance costs are often high. Submarine cables are also relatively difficult to maintain due to their hidden installation locations.

3. Environmental impact: the installation of submarine cables may have a certain impact on the marine ecosystem, and factors such as ecological protection need to be considered. If not carefully installed and maintained, it may lead to environmental damage and other problems.

4. Strong dependency: Once the submarine cable fails, it may affect the stability and reliability of the network connection. As submarine cables are a core component of network connectivity, any problems may affect the normal operation of the global Internet.

5. Security risk: Although submarine cables are relatively safe, there is still a risk of attack and damage. Some malicious actors may interfere with submarine cables, causing network communications to suffer.

Overall, submarine cables, as one of the main transmission methods of the Internet, have many advantages, such as fast transmission speed, high stability and large bandwidth. However, there are also some disadvantages, such as difficult installation, high maintenance costs, security risks, etc.. For units using submarine cables, they need to weigh their advantages and disadvantages and choose a communication method that suits their needs.