Could "Sea monsters" really exist...?

(Is this the right forum? Let me know.)

Do you think sea monsters could really be out in the ocean? Think about it. We don't know much about the sea. We know more about space than our own ocean. You know the mysterious underwater sounds such as SlowDown, Julia, or the most popular, The Bloop? Could those be the calls of an undocumented animal, or be proven?

What do you think? Or am I just rambling?

(I'm probably just rambling lol)