The only difficult part of this recipe is finding a container large enough to mix it in. I use the Tupperware Thatsa(tm) Bowl 32-cup mega mixing bowl, and I still had to mix it up in two batches.
Empty a 64-ounce bottle of ketchup into a large bowl. Juice the lemons and pour the juice into the ketchup bottle and swish it around to get the remaining ketchup. Pour it into the bowl and add bits of the lemon pulp. Stir in the horseradish.
Peel the cucumbers, but not completely See Photo. You want to leave some strips of the peel for color contrast. Slice in quarters lengthwise and remove the seeds. Cut the cucumbers into chuncks. Cut the celery into chunks about the same size as the cucumbers. Your cucumber and celery chunks should be close in size to your seafood.
Cut the bell peppers in half and remove seeds. Cut into thin strips. See Photo
Put the shrimp, artificial crab, cucumbers, celery and bell peppers into a jumbo mixing bowl. Pour on the cocktail sauce and mix well.
Cover the bottom of your serving dish with a 1-inch thick layer of the shredded lettuce. Spoon the seafood cocktail salad on top of the lettuce. Garnish around the side with slices or wedges of lemon.