The marine forecast definitions for visibility are:
Very poor - less than 1,000 metres
Poor - between 1,000 metres and 2 nautical miles
It was probably on the boarder line maybe just over 1000 meters at the entrance to the Hamble, normally there are clear views across Southampton water to Calshot and Cowes on the Isle of Wight beyond.
Swale Smack & Barge Match, 10th August 2019
2 hours ago