What this website is/was Skegness ASC (Amateur Swimming Club)
:Skegness is a seaside town and civil parish in the East Lindsey District of Lincolnshire, England.
It is possible that some time ago this site was hacked, but how/why you are getting redirected there is beyond me. I don't even know if the site is still active.
That said - If it happens again when the Avast Alert opens, use the See details option and it shows what is trying to reach it.
Most likely your browser (?) and not a bug in the AV as it has no reason to visit said site.
It could be an add-on in your browser that is trying to redirect to the site. Have you recently had any new browser add-ons or updated to existing browser add-ons ?
A google search for returns many hits, I did find this but it too is very old (so I wouldn't put much store in it being current, so I wouldn't recommend downloading anything):
https://tipsforoptimalbrowsing.blogspot.com/2015/09/removal-of-skegnessascorg-pop-up.html