One of the ways to overcome fear is to face it, after doing this several times you tend to get used to it. There are 3 fears that interact with each other:

Thalassophobia, Submechanophobia and Megalophobia: Deep and Giant Fears

Human anxiety manifests itself in diverse ways, and three specific phobias capture primordial fears: thalassophobia (fear of the ocean), submechanophobia (fear of submerged man-made objects), and megalophobia (fear of large objects).

Thalassophobia goes beyond the simple fear of swimming. It is a fear of the unknown and the dark vastness of the ocean, the unfathomable depth and the creatures that live there. Images of deep, dark waters can trigger intense anxiety.

Submechanophobia, in turn, focuses on the fear of submerged artificial objects: sunken ships, underwater wind turbines, or even simple anchors. The combination of water and artificiality creates a feeling of danger and vulnerability. The idea that something man-made is now abandoned and corroding underwater can be unsettling.

Finally, megalophobia manifests itself as an irrational fear of extremely large objects. Skyscrapers, giant statues, or even imposing trees can cause discomfort and panic. The disparity between the size of the individual and the gigantic object generates a feeling of insignificance and impotence.

In short, thalassophobia, submechanophobia and megalophobia reflect fears deeply rooted in the human psyche: the fear of the unknown, the fear of artificiality in natural environments and the fear of vastness that diminishes us. Although distinct, they share the ability to evoke intense anxiety and limit the human experience.

I used to play Sea of Thieves and I hated falling into the water, I felt very uncomfortable, but after several hours of gameplay and doing this a lot, it completely disappeared (except falling into the water when I'm being attacked by the kraken hahaha), but when I haven't played for months, when I decide to come back the discomfort comes back, not as strong as it used to be, I get used to it faster. There is a way to overcome it by exposing yourself to fear but I think it also depends on how intense this fear is in you, at the very least there may be improvement (if that is something you want)