You specialise in stabbing your food before passing it back to your grinding mouthparts further back, possibly crushing any shells or hard body parts with your legs on the way. You are pretty large and well protected and don’t have many predators yourself, so this is all looking pretty good.

You can survive for a limited time out of the sea, too. That carapace stops the sun from harming you, and you have simple flattened segments that efficiently extract oxygen from the sea water, and even a little bit from the air.

There’s a possibility that another food source might be available to you though. There are little wormies crawling around on land at the sea edge. You might find you do better to specialise in air breathing and hunting on land instead of in the sea. If you adapt to the air though, you’ll find that you can’t survive in the sea any more.