The Agassiz trawl or AGT is a sledge which is towed along the bottom of the sea at any depth. It is a very simple metal frame with a net behind to collect everything on the seafloor. Therefore it is perfect to collect animal from the seafloor to see who and what is living there. As it is very simple it has two major advantages: First it can be deployed to any depth up into the deep sea to 3000 – 4000m water depth as it has no electronics or pressure housings which could fail and secondly it can withstand quite a bit of physical impact like a rock or large bolder on the seafloor, again as it is just a metal frame and has no electronic parts to it.
The biggest disadvantage of such a simple system is that it is especially in deep water not easy when the sledge is on the sea floor and for how long you have dragged it. This makes it afterwards tricky to estimates for example of how much star fish are living in a certain area. As it is non selective it also will catch anything on the seafloor from the animal you are after to small rocks or even big boulders. These can partly destroy the catch when they move around in the net, so care has to be taken of how long the AGT has to stay on the sea floor.