"on the coast" vs "at the coast"

English as a Second Language English Teacher Explanations (ESL Tests)
1

I have heard on the coast and at the coast both used. I know on the coast is used more often in spoken English, but I have heard both used in different circumstances.
Thank you in advance for the information.

2

Hi Giovanni,

I’d go for ‘on the coast’ whereas ‘at the coast’ sounds a little bit informal/wonky to me.