hammering some things in the ocean seems impossible. all the character does is sail into the object, even if i click right on the edge of the thing. i can hammer stuff like bouys and fish farms, but the palace and reefs are no goes. if i want to break a reef, i have to use a boat cannon, which doesnt give me them lil nub things to make another reef.
also, not sure if this is worth mentioning, but this is a world linked with hamlet. thank you, i hope this helps!
try and hammer a chiseled coral reef/ballphin palace.