I see a lot of posts and comments about people getting killed instantly by everyday bandits and archers. The more experienced players recommend finding some harmless animal, wrestling it until all its limbs are broken and its teeth are scattered about, and just relaxing while the jellified creature attempts to push you to death. This is unnecessary.
Horseshoe Crabs have no arms to punch and scratch with, no legs to kick with, and no teeth to bite with. All they can do is push. And they litter the coastline like tourists in California.
A few extra tips: Lay down next to the Horseshoe crab to reduce your speed so it can get in more hits per turn. make use of the command-r and command-p commands to set up a macro for waiting. Set your attack settings to close combat so you don't accidentally wound the crab, and your dodge setting to stand ground so you don't hop out of range of the crab, and make sure you are out of range of the waves so they don't carry you away from the crab or visa-versa.
After one day of Crab-Grinding, you will be very difficult to kill. You will dodge or block most melee attacks, and ranged weapons will be easily dodged. Your fighter skill will also be well over legendary, so attacks with almost any weapon will hit even if you are unskilled in using it. Your strength, toughness, and dexterity stats will likely be superhuman, and several other important ones such as spatial sense will be at least above average. After five days, more-or-less the only thing that could kill you would be the mummy's curse combined with a large group of zombie and skeletal monsters. So stay out of tombs and catacombs, and you'll be just fine.
Warning Horseshoe Crab's push attacks can smash apart fragile bits such as toenails, fingernails, and ears. Smashed body parts cannot heal and will be infected, and as infections cannot be cured in adventure mode, this is a death sentence. So be sure to wear metal gauntlets, boots and a helm.