Coupled with the occasionally heavy rains and mild temps we've had extreme tides as well, which tends to refloat a lot of previously beached debris, and moves it farther as well. The larger rivers also add to the mess in heavy runoffs - we've seen literal "islands" of uprooted trees floating in Howe Sound after some of our classic subtropical-fed spring storms.
Things can definitely go "bump in the night"....
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)