Name an aquatic mammal

The rarest possible answer — almost no player finds it.

• Desman— Snorkel-nosed aquatic mole of Pyrenean and Russian streams.
• Water Opossum— Only aquatic marsupial; its pouch seals watertight when diving.

Genuinely obscure. Most players never think of it.

• Acrophoca
• Aegicetus
• Aegyptocetus
• Aetiocetus
• African Clawless Otter
• African Manatee
• African Marsh Rat
• Allodesmus
• Amazonian Manatee
• Ambulocetus
• American Mink
• American Water Shrew
• Ancalecetus
• Andrews' Beaked Whale
• Andrewsiphius
• Antaecetus
• Antarctic Fur Seal
• Antarctic Minke Whale
• Aquatic Genet
• Araguaian River Dolphin
• Archaeoparadoxia
• Arnoux's Beaked Whale
• Artiocetus
• Ashoroa
• Asian Small-Clawed Otter
• Atlantic Humpback Dolphin
• Atlantic Spotted Dolphin
• Atlantic White-Sided Dolphin
• Attockicetus
• Australian Humpback Dolphin
• Australian Sea Lion
• Australian Snubfin Dolphin
• Babiacetus
• Baiji
• Baikal Seal
• Baird's Beaked Whale
• Baird's Tapir
• Barasingha
• Basilosaurus
• Basiloterus
• Basilotritus
• Beaked Whale
• Bearded Seal
• Behemotops
• Blainville's Beaked Whale
• Bottlenose Whale
• Bowhead Whale
• Brown Fur Seal
• Bryde's Whale
• Burmeister's Porpoise
• Burrunan Dolphin
• Bush Dog
• California Sea Lion
• Caribbean Monk Seal
• Carolinacetus
• Caspian Seal
• Cetotherium
• Chilean Dolphin
• Chinese Water Shrew
• Chrysocetus
• Clymene Dolphin
• Commerson's Dolphin
• Common Dolphin
• Congo Clawless Otter
• Cornwallius
• Crab-Eating Mongoose
• Crab-Eating Raccoon
• Crabeater Seal
• Crenatocetus
• Cuvier's Beaked Whale
• Cynthiacetus
• Dalanistes
• Dall's Porpoise
• Deraniyagala's Beaked Whale
• Desmostylus
• Dhedacetus
• Dorudon
• Dusky Dolphin
• Dwarf Sperm Whale
• Earless Water Rat
• East African Wading Rat
• Elegant Water Shrew
• Enaliarctos
• Enhydriodon
• Eocetus
• Ethiopian Amphibious Rat
• Eurasian Beaver
• Eurasian Otter
• Eurasian Water Shrew
• European Mink
• False Killer Whale
• Fin Whale
• Finless Porpoise
• Fish-Eating Rat
• Fishing Cat
• Flat-Headed Cat
• Florida Manatee
• Franciscana
• Fraser's Dolphin
• Galapagos Fur Seal
• Galapagos Sea Lion
• Gandakasia
• Ganges River Dolphin
• Gaviacetus
• Georgiacetus
• Gervais' Beaked Whale
• Giant Beaked Whale
• Giant Beaver
• Giant Otter
• Giant Otter Shrew
• Giant Tapir
• Ginkgo-Toothed Beaked Whale
• Glacier Bay Water Shrew
• Gray's Beaked Whale
• Greater Cane Rat
• Grey Seal
• Guadalupe Fur Seal
• Guiana Dolphin
• Hairy-Nosed Otter
• Harbor porpoise
• Hawaiian Monk Seal
• Heaviside's Dolphin
• Hector's Beaked Whale
• Hector's Dolphin
• Himalayacetus
• Himalayan Water Shrew
• Hooded Seal
• Hourglass Dolphin
• Hubbs' Beaked Whale
• Humpback Dolphin
• Ichthyolestes
• Indian Ocean Humpback Dolphin
• Indian Rhinoceros— Wallows for hours a day to keep cool.
• Indo-Pacific Bottlenose Dolphin
• Indo-Pacific Finless Porpoise
• Indo-Pacific Humpback Dolphin
• Indocetus
• Indohyus
• Indus River Dolphin
• Irrawaddy Dolphin
• Jamaican Rice Rat
• Janjucetus
• Japanese Otter
• Japanese Sea Lion
• Japanese Water Shrew
• Juan Fernandez Fur Seal
• Kalakocetus
• Kekenodon
• Kob
• Kolponomos
• Kronokotherium
• Kutchicetus
• Lechwe
• Lesser Capybara
• Livyatan
• Long-Beaked Common Dolphin
• Long-Finned Pilot Whale
• Longman's Beaked Whale
• Lowland Tapir
• Lutrine Opossum
• Maiacetus
• Makaracetus
• Malayan Tapir
• Malayan Water Shrew
• Mammalodon
• Marine Otter
• Marsh Deer
• Marsh Mongoose
• Marsh Rabbit
• Marsh Rice Rat
• Masracetus
• Massoia's Lutrine Opossum
• Maui Dolphin
• Mediterranean Monk Seal
• Mediterranean Water Shrew
• Melon-Headed Whale
• Metaxytherium
• Minke whale
• Monk Seal
• Mountain Tapir
• Mountain Water Rat
• Nalacetus
• Narrow-Ridged Finless Porpoise
• Natchitochia
• Neoparadoxia
• Neotropical Otter
• New Britain Water Rat
• New Guinea Water Rat
• New Zealand Fur Seal
• New Zealand Sea Lion
• Nile Lechwe
• Nimba Otter Shrew
• North American Beaver
• North American River Otter
• North American Water Vole
• North Atlantic Right Whale
• North Pacific Right Whale
• Northern Bottlenose Whale
• Northern Elephant Seal
• Northern Fur Seal
• Northern Right Whale Dolphin
• Ocucajea
• Odobenocetops
• Omura's Whale
• Otter Civet
• Otter Shrew
• Ounalashkastylus
• Pachycetus
• Pacific Water Shrew
• Pacific White-Sided Dolphin
• Pakicetus
• Paleoparadoxia
• Pantropical Spotted Dolphin
• Pappocetus
• Peale's Dolphin
• Pere David's Deer
• Peregocetus
• Perrin's Beaked Whale
• Perucetus
• Pezosiren
• Phiomicetus
• Piscophoca
• Pontobasileus
• Pontogeneus
• Potamotherium
• Prorastomus
• Protocetus
• Puijila
• Pygmy Beaked Whale
• Pygmy Killer Whale
• Pygmy Right Whale
• Pygmy Sperm Whale
• Qaisracetus
• Rakali
• Ramari's Beaked Whale
• Rayanistes
• Remingtonocetus
• Ribbon Seal
• Rice Rat
• Rice's Whale
• Ringed Seal
• Risso's Dolphin
• Rodhocetus
• Rorqual
• Ross Seal
• Rough-Toothed Dolphin
• Round-Tailed Muskrat
• Ruwenzori Otter Shrew
• Saghacetus
• Saimaa Ringed Seal
• Sato's Beaked Whale
• Sea Mink
• Sei Whale
• Shaw Mayer's Water Rat
• Shepherd's Beaked Whale
• Short-Finned Pilot Whale
• Siamogale
• Sitatunga
• Smooth-Coated Otter
• South American Fur Seal
• South American Sea Lion
• Southern Bottlenose Whale
• Southern Elephant Seal
• Southern Right Whale
• Southern Right Whale Dolphin
• Southern River Otter
• Southwestern Water Vole
• Sowerby's Beaked Whale
• Spade-Toothed Whale
• Spectacled Porpoise
• Spinner Dolphin
• Spotted Seal
• Spotted-Necked Otter
• Squalodon
• Stejneger's Beaked Whale
• Steller Sea Lion
• Steller's Sea Cow
• Strap-Toothed Whale
• Striped Dolphin
• Stromerius
• Subantarctic Fur Seal
• Sumatran Water Shrew
• Sunda Water Shrew
• Supayacetus
• Swamp Rabbit
• Takracetus
• Tamanend's Bottlenose Dolphin
• Thalassocnus
• Togocetus
• Transcaucasian Water Shrew
• Trogontherium
• True's Beaked Whale
• Tucuxi
• Tutcetus
• Water Chevrotain
• Water Deer
• Water Mouse
• Water Rat
• Water shrew
• Water vole
• Waterbuck
• Web-Footed Tenrec
• Weddell Seal
• West Indian Manatee
• Western Water Rat
• White-Beaked Dolphin
• Yangtze Finless Porpoise
• Ziegler's Water Rat
• Zygorhiza

Uncommon — only a minority of players land here.

• Amazon river dolphin
• Baleen Whale
• Beluga
• Bottlenose Dolphin
• Capybara
• Dugong
• Elephant seal
• Fur Seal
• Gray whale
• Harbor seal
• Harp Seal
• Humpback whale
• Leopard seal
• Mink
• Moose— Dives to feed on pondweed, eyes open underwater.
• Muskrat
• Narwhal
• Nutria
• Pilot whale
• Platypus
• Porpoise
• Pygmy Hippopotamus
• Right whale
• River Dolphin
• Sperm whale
• Star-Nosed Mole
• Tapir
• Vaquita— Rarest marine mammal alive, under ten left in 2026.
• Water buffalo— Spends its afternoons submerged to the nostrils.

A solid, middling pick shared with plenty of other players.

• Beaver
• Blue whale
• Hippopotamus
• Manatee
• Orca
• Polar bear— Officially a marine mammal; it hunts from sea ice.
• Sea lion
• Sea otter
• Walrus

The most common answer on the board.

• Dolphin
• Otter
• Seal
• Whale