And some who bought rights to wrecks from Lloyds called themselves wreckers. 'Above I mentioned the Robert Louis Stevenson novel, The Wreckers, in which a salvor buys a wreck at the Lloyds auction for a surprisingly large sum of money. Haven't read it in years, but it is on my reading table and I will get to it soon.

To some extent the terms were interchangable among common folk and sailors; the Wreck and Salvage Acts define the terms.
Interesting are the definitions of wreck and salvage in an Act of 1887, applied in the Pacific, Fiji.

"This Act may be cited as the Wreck and Salvage Act."
[brief extracts]
"Comptroller" means the Comptroller of Customs and Excise"
"wreck" includes jetsam, flotsam, lagan and derelict found in or on the shores of the sea or any tidal water;
"salvage" includes all expenses properly incurred by the salvor in the performance of the salvage services.

4. When any ship or boat is wrecked, stranded or in distress at any place on or near the shore of the sea.... the receiver shall ...forthwith proceed to such place and upon his arrival there take command of all persons present and assign such duties...and issue directions ...with a view to the preservation opf such ship...lives...cargo and apparel thereof, and if any person wilfuly disobeys ...
6. All cargo and other articles belonging to the ship..that may be washed on shore,,,etc. shall be delivered to the receiver...
7. .....any person plunders, creates disorder and obstructs....the receiver shall cause such person to be apprehended...
8. [If, in caring for persons from the ship, cargo, etc., the receiver and his assigns may cross adjacent lands without being subject to interruption by the owner...
Etc., etc.

Interesting!
http://www.paclii.org/fj/legis/consol_act_OK/wasa152