Old manual inflatable lifejackets.

[Boathook]

Thigh straps are only there to prevent LJ from rising up and causing victim to have face below water ... they are not designed to support lifting of the victim. The jacket fit itself is designed to carry out that function ... trouble is too many do not actually wear it secure enough ...

Having watched an recorded episode of Saving lives at sea last night, it showed a kayaker being hauled out of the water. He had a buoyancy aid on but that nearly came off as he wasn't really able to help himself due to cold.
Possibly a requirement for straps on buoyancy aids.