The mother sea whelk is a huge sea whelk who only appears in the episode "Whelk Attack," when she is raising her whelk kids and terrorizing Bikini Bottom.
The mother sea whelk is a very large snail with a light orange spiky shell and light purple skin. Her children are often seen with her with the same appearance but smaller. She has yellowish-white pointy teeth as well. She can inhale and use her long tongue to eat something she desires. She can also exhale purple bubbles/goop.