Inspect 1 large jar for cracks. Immerse in simmering water until cucamelons are ready. Wash a new, unused lid and ring in warm, soapy water.
Place cucamelons, chile peppers, dill, yellow mustard seeds, dill seed, and peppercorns in the sterilized jar.
Combine water, vinegar, and salt in a saucepan and bring to a boil. Stir until salt has dissolved, about 1 minute. Remove from heat and let cool
Pour vinegar mixture over cucamelons so they are completely covered. If you don’t have enough liquid, mix equal parts water and vinegar and add to the jar. Close jar with the lid and let stand 3 to 4 days.