Suffering from aquaphobia, Sonic is incapable of swimming and sinks in water. He is also unable to utilize his speed properly on certain types of terrain, such as smooth ice, although he has the Blue Force One to make up for such situations.

Is Sonic scared of water?

As far as how he obtained it, I think at some point in his life, Sonic has had a very negative experience with water, which virtually impacted his entire outlook on even so much as getting wet.

What are Sonic's fears?

This video reveals that Sonic has arachnophobia, which is a fear of spiders.