The Ambergris Element (episode)
The crew of the Enterprise explore a submerged culture on a water world.

Summary
"Captain's log, stardate 5499.9. We are orbiting the planet . Argo was once a land planet, but its surface is now almost completely covered by water. The change was caused by violent seismic disturbances. Our mission is to study the effects which the quakes and other phenomena had on its surface. This knowledge may save millions of lives on a Federation planet, identical to Argo, which will soon be undergoing similar transformation."

The crew lands on the water in a specially designed aqua-shuttle, but this immediately comes under attack from a giant sur-snake. After the creature is fired upon by the aqua-shuttle's onboard phasers, Captain Kirk orders that the shuttle submerge and take a closer look at it before the stun wears off. The creature quickly regains consciousness however, and continues its attack. Kirk opens his communicator and asks Scott to beam them up, but the sur-snake grabs the shuttle and throws it against the rocks. Lieutenant Clayton and Dr. McCoy are thrown clear and fall into the water, but Kirk and Spock are still in the shuttle and disappear when the vessel submerges in the being's grip. 

"Ship's log, stardate 5504.2. Lieutenant Commander Montgomery Scott in command. Captain Kirk and First Officer Spock have been missing for almost five days. Search parties can find no trace of them or the aqua shuttle. Dr. McCoy and I are continuing the search at a greater distance from the attack point."

McCoy, Scott, and Lt. Clayton find the missing officers, both with strange mutations.

"Medical Log, Stardate 5506.2. Captain Kirk and First Officer Spock were rescued forty-eight hours ago. They have no recollection of what happened to them after they were attacked, but medical examinations show an unidentified substance in the blood stream has affected their entire metabolism and changed them into water breathers. Their internal structure is completely transformed, and even their eyes are covered with a transparent film, like the second eyelid of a fish. So far, all efforts to return them to normal have failed."

Kirk and Spock are inside a tank filled with water. McCoy says through an intercom, "We're stumped, Jim. The hormone seems to be the major factor in your mutation, but we just can't identify it." Kirk asks, "Are you sure the mutation wasn't somehow accomplished naturally?" McCoy replies, "It's infused into your bodies at key structural points. It had to be done by injection." Kirk demands, "But can't you duplicate it, Bones? Your medical computers have information of every procedure in the Federation's hospitals." McCoy says, "It's highly sophisticated, and completely unknown to us." Spock inserts, "That implies there are intelligent lifeforms on Argo." McCoy replies, "The sensors don't indicate any lifeforms down there aside from fish." Spock thinks the readings may be incomplete. Since Kirk cannot spend the rest of his life confined to a tank, least of all command the Enterprise from inside one, he and Spock are forced to return to the planet and travel underwater to find the planet's inhabitants, whose name for themselves proves to be "Aquans," in the hope that these will be able to return them to their normal Human and Vulcan selves.

Kirk and Spock explore the submerged Argo and find a group of inhabitants who hate and fear air-breathers. They want them to leave. Their young saved them once but it will not happen again. The two officers soon find a beautiful underwater city and are promptly taken prisoner. Hesitantly, the Aquans agree to perform surgery to return Kirk and Spock to normal, but when Scott dives down to warn of an impending quake, they become fearful of air-breathing spies. Kirk and Spock are deemed treacherous and are sentenced to death by forced suffocation.

Rila, a water breather, agrees to help them if they will in turn help her find a buried ancient city in ruins whose archives may contain a way to reverse the mutation. They discover that the substance in their bloodstreams is similar to the ambergris of Earth whales. The reverse mutation is induced by an infusion of an antitoxin made from the venom of a deadly giant sur-snake. The Aquans help them obtain the necessary medicine, but Kirk nearly dies from the vaccination.

In orbit, the  uses its phasers to blast uninhabited sections of the planet in an attempt to move the quake's epicenter away from the Aquan city, and also causes an inadvertent side effect: new land masses emerge from beneath the oceanic surface. Grateful for saving their lives, the young Aquans make their ancient records available to the Federation and inexplicably decide to use the newfound medicine to become air-breathers themselves and resume life above-ground. Kirk implores them not to lose contact with their underwater ancestors. The elders declare they will pass ordinances to forbid that and this time they will not ignore them.

Log entries 
 Captain's log, USS Enterprise (NCC-1701), 2269
 Ship's log, USS Enterprise (NCC-1701)
 Medical log, USS Enterprise (NCC-1701)

Memorable quotes
"What the devil was that thing?"
"Apparently a lifeform which previous surveys have not recorded."
 - McCoy and Spock

"We've lost contact, captain. Repeat, we've lost contact. Come in, captain, come in!"
 - Scott

"Their bodies are functioning. Metabolism, heart, everything but the lungs!"
"Can't breathe… suffocating! Help! Can't breathe…"
"What happened to them doctor? What is it?"
"Something's changed their whole lung structure. They can't live in the air anymore!"
 - McCoy, Spock, Scott, and McCoy again

"Our equipment is too limited."
"We aren't limited. We can go wherever we want in that ocean."
 - McCoy and Kirk

"Look at this place… a tank! I can't command a ship from inside an aquarium – I can't LIVE in here!"
 - Kirk 

"It is quite possible, captain, that they find us grotesque and ugly and many people fear beings different from themselves."
 - Spock

"Apparently, they were exposed to a frightening geological disaster. Such hardship induces savagery and violence."
 - Spock, on the Aquan's distrust of air breathers

Background information

Story and production 
 This episode's writer, Margaret Armen, also wrote , as well as the scripts for  and . She remembered how she came to write this installment; "[Story Editor Dorothy "D.C." Fontana] approached me. I thought it would be fun." Armen also expressed that this episode (in common with "The Lorelei Signal") was indeed fun and that she enjoyed doing it. (Captains' Logs: The Unauthorized Complete Trek Voyages, p. 98)
 As  vocal specialist, James Doohan did the voices of six characters in this episode. In fact, this is one of two episodes of the animated Star Trek series that Doohan provided the most voices for (the other installment being , for which Doohan voiced seven characters).
 D.C. Fontana has repeatedly cited this outing, with its extensive use of underwater scenes, as an episode that was only possible because it was produced in animation rather than live-action. (; )

Continuity 
 This episode introduced two water-themed landing craft – the Enterprises aqua-shuttle and the scouter-gig – for the first and only time.
 Scott uses a life support belt, rather than a diving suit, in this episode.
 The NCC-1701\5A aqua-shuttle was the first armed shuttlecraft to appear in Star Trek.

Reception 
 The editors of Trek magazine collectively scored this episode 2 out of 5 stars (a rating that they termed "fair"). (The Best of Trek #1, p. 110)
 In The Star Trek Files magazine, John Peel remarked, "A particularly silly story, even for Margaret Armen. The concept of changing surface-breathers into mermen is an old one, generally discarded by serious sf writers without staggering technological innovations. Somehow, a series of injections from venom hardly seems appropriate! It's such a pointless story, just another in the line of 'let's do something you couldn't do on a live show,' without much [thought] […] to it. Isn't it convenient that there is a way to reverse the operation? And that it works so fast on humans? Actually, there's one really silly line, where they refer to the antidote as an 'anti-toxin', showing that the production staff thought that the two words are interchangeable. An anti-toxin only works against poisons, and neither Kirk nor Spock were poisoned! One nice thing about the story is the use of yet another specialized shuttle, this one adapted for undersea work. It's [a] logical extension of the Enterprises equipment, and very handy for exploring a world such as this." (The Star Trek Files: The Animated Voyages End, p. 21)
 In the unofficial reference book Trek Navigator: The Ultimate Guide to the Entire Trek Saga (p. 7), co-writer Mark A. Altman rates this episode 2 and a half out of 4 stars (defined as "average") while fellow co-writer Edward Gross ranks the episode 2 out of 4 stars (defined as "mediocre").
 In 's "Ultimate Guide" (), this episode was rated 4 out of 5 Starfleet arrowhead insignia and was deemed the fifth best installment of TAS. The magazine considered, "A shuttle designed to go underwater, a tentacled sea serpent, and Kirk and Spock transformed into water-breathers… what more could you want? Perhaps Scotty piloting a high-tech motorboat for a search party and an underwater civilization of mermaid-like Aquans? Another great use of animation to tell a big Trek story."

Video and DVD releases
UK VHS release (CIC Video): Volume 4, catalog number VHR 2538, 
As part of the The Animated Series LaserDisc collection
As part of the The Animated Series DVD collection
 As part of the The Animated Series Blu-ray collection

Links and references

Starring
William Shatner as Captain Kirk
Leonard Nimoy as Mr. Spock
And
DeForest Kelley as Dr. McCoy

Also starring
Majel Barrett as
Aquan female #1
Rila
Aquan female #2
Aquan female #3
James Doohan as
Arex
Cadmar
Cheeron
Clayton
Domar
Scott
Lou Scheimer as
Lemus
Aquan harvester
 Unknown actor as
 Nephro
 Aquan male
 Aquan guard

Background characters 
 Chapel 
 Sulu
 Uhura
 Science division landing party member
 Four other Aquan harvesters
 Five additional Aquan Tribunes
 Three other Aquan guards

References 
air; air-breather; algae; ambergris; ancestor; answer; antitoxin; Aqua-City; Aquans; Aquan city; Aquan ordainments; Aquan ancient records (Aquan knowledge records); aquarium; aqua-shuttle; architecture; area; ; Argo-like planet; assistance party; attack point; backpack; big island; blood; bloodstream; body; "Bones"; boulder; building; chamber; chance; choice; civilization; clothes; cold; composition; consciousness; contact; contact range; continental shelf; coordinates; creature; damage; day; Denebian whale; devil; directional marker; distance; dizziness; dose; drowning; Earth; Earth whale; edibles; effect; emergency; enemy; engineering officer; entrance panel; epicenter; evolution; exile; experiment; exploration; eye; eyelid; Federation; fern; fern bed; fish; friend; geological disaster; gills; "go away"; gratitude; hatch; heart; heartbeat; hereditary trait; High Tribune; hormone; hospital; hour; infusion; injection; instinct; intelligence; ; Junior Tribune; justice; key; knowledge; land; land mass; legend; lie; "like blue blazes"; life support belt; lifeform; light; logic; lungs; medical computer; medical examination; medical symbol; memory; memory wipe; mesh; metabolism; mile; Milky Way Galaxy; million; minute; mission; mountain; mutation; name; NCC-1701\5A; NCC-1701/R6; north polar seas; ocean (sea; open sea); "of course"; ordainments; peace; peak; phaser; phenomena; phrase; place; place of safety; population; power pack; pressure area; pressure force; proof; pulse; recollection; reef barrier; rescue; respiratory system; rock; rocky outcrop; ruins; Ruling Tribunal of the Aquans; savagery; scientist; Scots language; scouter-gig; sea bottom (seabed); sea foliage; sea level; seaquake (tremor); search; search party; seawater; scientist; seismic disturbance; sensor; serum; shelter; skeleton; specimen; speculation; speed; spy; "stand by"; strength; suffocation; surface; surgo-op; surgo-records; sur-snake; survey; ; "take care"; ; telefocals; thing; thought; tides; time; topography; torso; transformation; tribune; universal translator; value; venom; visitor; "wait a minute"; water; water-breather; water mask; weapon; web; whale; "what the devil"; world

External links 
 
 
 
 

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fr:The Ambergris Element (épisode)
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Ambergris Element, The