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MFF Sea Beast Week: Breaking Down the Mariner vs. Sea Beast Moment in Waterworld

July 24, 2018

Welcome the MFF’s Sea Beast Week! This article was originally published earlier this year but we brought it back because it’s pretty great.

Kevin Costner killing the Sea Eater in Waterworld has long been a scene that I’ve been obsessed with. I wrote about the Sea Eater in 2015 and Waterworld has been featured in my jet ski action scenes are the worst, and people getting swallowed whole and surviving posts (it’s random I know). I’ve always loved the idea that someone can jump into the water and be attacked/swallowed whole in a span of 20 seconds. The biggest problem I’ve always had is there is no way he would be able to stay attached the rope he was trolling on. Thus, his boat would sail away whilst he was trying to free himself from the innards of a giant monster. This means he would have to use his super swimming abilities to catch up with the boat, turn it around, and then cut the meat off of the sinking monster.

Here is a breakdown of the scene.

Costner (AKA Mariner…AKA Grumpy Costner) gets annoyed that the women on his boat are actively trying to feed themselves via fishing, so he grabs their fishing poles and throws them into the water. After throwing away his gear, he grabs some supplies (speargun, rope), turns on the boat’s trawling engine and jumps into the water (:46). Once the rope is fully extended he starts stroking the water gracefully in an effort to lure prey. Something underwater sees this display of graceful swimming (1:09) and thinks it has found dinner. The large beast surfaces and swallows Costner whole (1:20) and Costner ends up murdering the beast from the inside. Then, Costner cuts off roughly 100 (being generous) pounds of meat and three people feast.


This scene left me with several questions:

  1. Why was it so easy to kill a monstrous sea beast?
  2. Had he killed large creatures before?
  3. Why did he throw away his fishing poles?
  4. If large sea beasts are plentiful, why would people ride jet skis?
  5. What happened after the death and before they ate?

After scouring the internet for data on the Sea Eater, I learned that people don’t know much about it (I got zero responses from people who read the novelization). I have nothing to go with in regards to the monster and Costner’s past hunting, so I decided those questions will be left unanswered. What I can fill in is what happens after the monster eats Costner and before they gorged on delicious looking meat.

Here is what we know so far:

  1. It took eight seconds for the 40-foot rope to become taught after Costner jumped into the water. This leads me to believe the boat was moving at a leisurely pace of 3.41 miles (2.96 knots) an hour.
  2. He turned on his trawling motor before he jumped into the water. However, he didn’t use the cable attached to the winch on the back of his boat.
  3. According to the Sea Eater is 40-feet long and weighs an estimated 20 tons.
  4. During the sea atoll attack earlier in the film, Costner covered 120-feet in eight seconds. That comes to 10.2 MPH which means the dude can fly in the water. I came to 10.2 MPH by finding a picture of the atoll, measuring the boat (60 feet long), and then measuring the distance from where he jumped.
  5. Costner let go of the rope after the monster attacked. I know this because the boat would’ve stopped momentarily and the rope would’ve split in two if he held on. There is zero chance a tiny rope could withstand the force of a moving boat and a suddenly dead 20-ton monster (watch this clip of a marlin sinking a boat for proof of what would happen if the beast lived).
  6. Since there is no sign of salt or proper drying methods, I’m assuming Costner only took as much as he could carry for one or two meals maximum. This means that at least 39,900 pounds of sea eater meat was left behind for other hungry sea denizens.
  7. It was dusk when they started eating the food. This makes sense because he had to heat up the charcoals and prep the food.
  8. The scene reminds me of a Mitch Hedberg joke

Mitch Hedberg@M_Hedberg

On fishing shows, they catch the fish and then let it go. They don’t want to eat the fish, they just want to make it late for something.


Here is what happened after the monster was murdered:

  • After watching various clips where people have to free themselves from dead/animatronic animals I’m guessing Costner (and his super powers) needed two minutes to free himself from the innards of the monster. It was clearly sinking, blood must’ve been everywhere and stomach lining is a beast to crawl through (not speaking from experience). He also had to secure his gun because he could not super swim with it.

  • By adding the original Costner/boat distance and time it took to free himself, secure his gun, and start swimming I’m thinking the boat was 715 feet ahead of him (40 + 600 + 50 +25 = 715).
  • The women on the boat must’ve been justifiably shocked as to what had transpired. So, in their shock, the boat floated far enough away for them to not hear anything Costner might’ve shouted. We know Helen could steer the boat, but after the shock wore off, the process of turning the boat around would’ve been a beast of a job. I’m also guessing that Costner was still grumpy about losing his spear gun from earlier so he swam to the boat and did everything himself.
  • Knowing the creature was sinking, Costner started towards the boat, and since he could move at three times its speed he only needed 75 seconds of super swimming to catch up.


  • He turned the boat around and made his way back to the sea monster. He would’ve needed AT LEAST seven minutes to turn the boat around, travel back to the monster and anchor the boat. I’m guessing he was able to speed up the 1,840-foot return journey which would cut down the trip.
  • He dove down to catch the sinking beast. I don’t know anything about the floating tendencies of dead 20 ton monsters with holes in them, but it seems likely that it would sink because there is no way gasses could build up because of the massive holes in it (Thanks research!).


  • He prepped the diving bell (watch underwater Denver scene) and gathered supplies (five minutes) and dove to the bottom of the ocean to cut off some prime meat and potentially fist fight another creature (eight minutes). After watching various clips of chumming it’s evident that the majority of the stuff that exploded would’ve sunk by the time he returned.
  • He swam back up and put all of his gear back in place because he is particular like that (eight minutes).
  • The cooking started (30 minutes to heat grill, at least 30 minutes to heat massive meat steaks).
  • They ate!


After breaking down all the variables (known and unknown) the entire process before cooking everything would’ve taken AT LEAST 32.25 minutes because Costner had a lot to do before he could even start preparing the food. This may sound like a lot of time, but it’s not too bad when you consider the killing, swimming, boating, prepping gear, swimming, cutting, more swimming and putting away gear.

There you have it! The full breakdown of what happened after the killing and before the cooking. You can rest easy knowing that you will never have to spend another sleepless night thinking about what happened!


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