This is a Mechanical Rock Grapple suitable for Cranes for marine projects. 

The main application is taking out heavy rocks from the bottom of the water.

These four-finger mechanical grapples are normally used on cranes, these can be used both onshore and offshore for dredging underwater and also lifting and dumping boulders, heavy rocks for stone pitching, and other jobs such as handling scrap material for loading and offloading.

This attachment is coming in different configurations depending on loading capacity, and the type of operation where these are going to be used, they are also designed as five and six-finger mechanical grapples for cranes too.