Grab (tool) Wikipedia
A grab is a mechanical device with two or more jaws (also called clamshells), used to pick things up or to capture things. Some types include:Roundnose grab
in Dutch and German they are called poliep grijpers/ Polypengreifer = "polyp grabs".
There are different ways of open/close the grabs:electro-hydraulic / diesel-hydraulic
mechanical by rope(s) (1-rope, 2-ropes, 3-ropes, 4-ropes)
Grabs can be used for:dredging
bulk handling (e.g. loading/unloading ships)
salvage (e.g. ship-wrecks, oil)