Admiral insurance are giving all car policyholders £25 a car because claims have been so low.
My boat insurance with GJW went down this April from £373 in 2018 and 2019 to £250.
I would think there is significant extra risk of damage from people not checking their boats.
You might buy 'laid up' insurance, but that's often not a whole lot cheaper.
Paying extra for racing risks might not be good value right now.
One non marine insurer I know is paying staff to send out renewal notices but a lot of policies are not being renewed.
I have no evidence for this assertion, but I would hazard a guess that more boats sink at their mooring or as a result of breaking free, than are damaged by their owners while out sailing or pottering about in a marina.