To be sure it’s still used for marine navigation, you’d have to look on a current chart. I’d go as far as assuming it is still current if it can be seen from the sea. If solid , not moving objects can be seen from sea, they get used. This has even included trees for ad-hoc transits. I’ve even seen people select cows! When conditions change that affect navigation, markers, buoys etc. do get moved and information issued via ‘Notices to Mariners’ for charts to be updated manually.
One of my local marine approaches is a white pillar in front of a white wall with an unpainted vertical strip. When the strip and pillar are aligned to see all white, you’re on the deeper channel. A few metres either way and you’re aground at low tide.
Edited for ‘current’