The Bailiwick bubble – allowing Bailiwick residents to travel freely between the different islands – was set up early last month.
But Guernsey visitors have not been enough to plug the hole left by UK tourists in the smaller islands.
Sark reopened to Bailiwick visitors on 1 June, while Herm welcomed visitors from 9 June.
There were 1,560 people travelling to Sark during June, compared with 7,669 last year – an 80% drop.
Herm saw a 73% drop compared with last year – from 10,662 down to 2,871.
Alderney’s ferry service – which is run by the Little Ferry Company – has seen a much smaller drop, from just over 1,000 down to 564.
There are still self-isolation restrictions for anyone returning from outside the Bailiwick, and this has resulted in ferry services to Jersey and the UK still being very limited.
There were 22 people travelling between the Bailiwicks last month, and 70 people who travelled between Portsmouth and Guernsey.
Overall, 5,000 people travelled through St Peter Port’s port last month, down from 60,000 in June 2019.
There were no sailings from Poole, which is usually the port’s biggest market, making up a quarter of all passengers to and from Guernsey by boat.
There have also been no commercial sailings between the island and France.