This is a Select Viper Speed fin that I bought second hand.

Upon inspection I noticed the hairline crack that you can see in the attached picture, and it looks to me like that's a pretty serious crack that could deposit my fin into the water unwantedly pretty soon...

Is it serious like I think it is? And is there a way to fix this?

This fin took 2 months to arrive from my country to Boracay where I currently live so if I would order another fin the season would already be over. So I need to make things work with this fin.

Any tips? How can I fix it or at least make it last longer?