@BC Coast Pilot correct me if I'm wrong. PFDs are only required outside the cabin. Might depend on the vessel rating.
Below is opinion only, not advice.
Correct, Unless under 16 for pleasure where it must be worn at all times. Otherwise, when on deck or outside the cabin, and there is also a difference between when working and pleasure regs. And of course vessels rated where you don't have to wear it at all, such as a passenger vessel, with rated railings etc. A rowing skull etc.
For pleasurecraft:
"Transport Canada’s Small Vessel Regulations (the Regulations) require that an approved PFD or lifejacket of an appropriate size be carried for each person on board a recreational vessel, but the Regulations do not require them to be worn, except in limited circumstances".
This is the pleasure policy below that requires MOST of us to wear an inflatable pfd on deck IF that's all you have and don't carry proper jackets.
To improve safety by promoting the constant wearing of comfortable and effective alternatives to lifejackets on certain small commercial vessels operating in certain bodies of water.
tc.canada.ca
There are lots if us in the marine trade that live on these vessels for days/weeks at a time and I ain't wearing one while in the seat or the rack or eating. There is an SSB for workboats less than 15 tonnes (day boats) that refer to "at all times when underway" which is probably where we see the difference, for little RIBS and the like that we see day to day.
""commercial vessels that are less than 15 gross tonnage and operating within near coastal voyages, Class 2, PFDs must:
be approved by Transport Canada or the Canadian Coast Guard
always be worn when underway:
In an open boat
on deck, or
in the cockpit on a vessel of closed construction"
I think MOSH defines it as "where there is a risk of drowning" The language for inflating vests is different from regular vests also. Whereas the inflating vest "must" be worn on deck outside the cabin the regular vest does not for pleasure. I carry both types to mitigate that on my pleasure craft.
With the work jacket, similar to being in a helo crash, you don't want to be pinned inside a vessel with your inflated vest holding you against a bulkhead when trying to escape, although you're gonna be reassured which way is up while you slowly die. Having your safety equipment trying to kill you or during lunch must suck (they do go off at the most inappropriate moments)
Vessel transfers are covered by another section yet again and Pilot boarding arrangements are covered under SOLAS
This is where our training shines (the transfers), for both the vessel to vessel and Helo transfer safety
Commercial fishing vessels are yet another category.
So, the answer to your question is a bunch of questions about vessel specifics, size and category. The ultimate being the vessel class and GRT. Please refer to vessel certificate.