Originally Posted by MarkofSeaLife
No, the boat should have tethers. But it wouldn't hurt to ask if he has a harness for you.
So if you can keep yourself warm and dry he should keep you safe.
What he/she "should" do and what he/she might do to ones own satisfaction are two different matters, eh Mark?
It would be wise to include a tether, preferably doubled (with a long and short leg), in your kit that you know you can rely upon. Likewise, you might include your own personal survival gear that can be attached to and perhaps enclosed within a pouch on the webbing for your PFD (which should include a crotch strap) including a small strobe, mirror, pencil LED flashlight (or LaserFlare), waterproof hand-held VHF (with fresh batteries and wrist lanyard) and perhaps an ACR (or equal) PLB.
When taking crew-mates aboard for a passage, we forward them a listing of what equipment we expect them to supply for themselves and what we have aboard the yacht. Never-the-less, supplying one's own personal safety gear only makes sense, no?