It's a 41 footer so in most cases it has V-drives. If that's the case it's blow air in the strainers and then shut the seacock. Drain and for the most part your done. If it does have outdrives, then the hose is pulled off the seawater pump and lifted above the water line and tied off. Many attach a piece of PVC pipe to the hose to give it more height to tie off. Use the hose clamps to secure the hose to the pipe. Around here this is how they do them most often. We still have some using antifreeze but that's a different story.
If they were just winterize and there is no fowl play, then either something wasn't done correctly or something broke. Maybe hose lifted up but forgot to tie off and it dropped. Had one sink here last year because the winterize'r stepped on a fitting and broke it getting out of the boat with his foot. This is still in litigation with the insurance company but not with the owner, he went from a 32 footer to a 50 footer.
