Live with (if it doesn't leak) or replace.

You’ve learned one of the major downfalls of a fire clay sink. They’re not highly recommended for that reason...they‘re not forgiving, and crack easily.

Perhaps the forum sink expert, Joseph Corlett, will have an idea for you. Hopefully, he’ll see this.

You can epoxy it to hold water for a while, until (if) you can find someone to replace it. It won’t be a pretty fix. It cannot be “repaired”.

Where is the crack? I can’t see it in the pic.

The crack is faint but definitely there. It's a "u" shape - I added a yellow dot at the beginning, middle and end.

"... sink so you don't have to remove counters?"

Countertops aren't removed for sink replacements.

I'd dribble some super glue in it to try to hold back contamination and hope it didn't leak, but there's no fixing it with a spray on coating, only replacement.

There are so many other beautiful options that don't involve fireclay if you replace, so don't be discouraged. I did a lot of sink research and settled with an apron-front workstation sink from Havens Metal and am so pleased with it. They can give you a custom size in copper or 316 stainless. Their texture finished are really pretty, and you'll never have to worry about fireclay damage again.