I have thalassophobia. It is the fear of those who may live in the depths of lakes/seas. When I was little, my parents and I went to Karelia. There is a lake there, in which during the Second World War, a tank and a large number of soldiers drowned (according to local residents). I have never experienced such animal fear as that day. This lake was so black that I could not see its bottom even close to the shore.
Since that moment, I have been terribly afraid to go into the water and can only swim in pools. My fear was so strong that for the first few years I had sleep apnea, where I had dreams where I was swimming in lakes. Now I stopped having such dreams and stopped swimming in the lakes. But when I think about something floating under my feet and someone looking from the depths, I get scared again :(

I couldn't translate my thoughts on my own, it was too difficult. Therefore, I used a translator, I hope that this description does not lose its meaning.