At least in the US, the coast guard does not want a float plan filed, until they need it to find you.
If it is a large happening, they may want you to have a marine event permit, which is a float plan on steroids. This is more likely in areas with active boating (Golden Gate Sea Kayak Symposium had to get one).
More common seems to get to have ground support connected by InReach, Spot, Sat Phone, etc. That person would have all the float plan info and be the most likely one to call if you don't check in.
Myself and another guy (Anders) were the safety support for
Matt Krizan when he paddled the entire California Coast (link to Men's Journal article) about 10 years ago. He had an InReach and that was what we used to contact him. He used 2 of us both as duplicate (in case one of us wasn't available on a day) and also to double check - Anders and I both independently sent Matt weather/surf reports and if Anders and my predictions were off, Matt would start asking questions.
Matt used the breadcrumb feature, so we would see every 10 minutes or so where he was. He would also check in each night with us by text after he landed and got settled.
One night at the southern end of Big Sur (so north of Morro Bay), one of Anders and I noticed that his break crumb track ended short of the beach, but not on the beach. And he hadn't checked in yet. So we started talking with each other and deciding what to do, inclduing whether to call in the authorities. We came to the conclusion he was likely Ok, so we'd wait to see if he checked in. If he crashed and burned on landing (most likely problem at that point), the chance of his InReach dying at the same time seemed small, so we'd expect it to still transmit. In the end it just was that Matt turned the InReach off shortly after landing to save batteries. He thought he left it on long enough so we'd see he landed.