I was quite surprised that this website seems to use a self-made map viewer. Maybe I'm just out of the loop, but it feels like by now everyone either just uses Google Maps and a minute, hardy fraction uses something based on OSM.
https://www.vesselfinder.com/aismap?zoom=8&lat=36.00&lon=-5....
Kind of stupid design, as the [i] button is so big that a small always visible attribution could have fit better (just like on osm.org).
This is seemingly one of default options in OpenLayers (my guess based on how often I see this type of attribution). I wonder why people choose OL anyway. Sites using it in my experience have on average jankier UX than those based on Leaflet.