So they found a massive amphipod over 4 miles deep in the Kermadec Trench off New Zealand. A good sized amphipod is usually a few centimetres long (an inch) but this thing is 28 cm (almost a foot)! And that's the biggest one they managed to drag up, they actually spotted on camera one that was 34 cm (over a foot) long.
Aside from that, they got a great sense of smell and gorge themselves on whatever scraps of rotting flesh make it to the seafloor. They got expandable stomachs to help them stuff themselves and some of them can then fast for a year. This is NOT a healthy way to diet.
This Amphipod pretty much looks like a big version of most of the tiny ones. Our very own Skeleton Shrimp is an unusual kind of amphipod. For me, a 1 foot tall Skeleton Shrimp may not be THE Holy Grail, but it's certainly A Holy Grail. (Quite a lot of the other Holy Grails are probably even bigger Skeleton Shrimps.)
But how did it get sooooo big? Dave Hubble's got a cool (freezing cold) post that explores the issue. He mainly centres it around a specific (massive) Sea Spider, but a lot of the same questions arise. It's always interesting when no-one is quite sure how good things happen!