Man has tried but its not as easy as the space. Many research has been conducted but they failed. Sending a signal to the space to get some information seems easy than sending it into the depth. In fact when they tried it, the signal got distorted by wave and it didn't get anywhere in the ocean.

It was said that two men traveled 5hours into the sea depth to know and gather information but they came with nothing tangible. The silence about the research on Ocean is why people think man isn't doing anything about it but research is going on daily. The Mariana trench in USA is full of men carrying out research every day to know more about the ocean and its environment.

If it were as easy as space, I'm sure man would have found a place where we can live and survive in the ocean.