Introduction: RC Shark Boat Prank

Picture of RC Shark Boat Prank

DA dum... DA dum... DA dum... DA dum

SHARRRK SHAAARRRK!! SHARR oh, wait... never mind... sorry.

Here's how to easily turn a remote control boat into a shark fin to scare your friends at the beach. This is a good project for people who like making a mess and for people who like seeing their friends scream.

For this project, I used the following materials.

One large RC Boat

Cardboard and masking tape (for molds only)

Acrylic sheet

Spray foam insulation




Step 1: The Boat Lid

Picture of The Boat Lid

This step is optional and will probably be unnecessary or difficult with some boat models. The top of the boat I got on Amazon had some large speedboat features on it that I suspected would get in the way of the shark features, so I decided to create a new lid for it before commencing with the shark fin build. I traced the original lid on a piece of acrylic and cut out the shape with a band saw. The new lid had a bonus benefit of being more rigid than the original and easier to seal to the boat with foam rubber tape.

Once your new lid is cut out and inserted, cover the rest of the top surface of the boat with painters' masking tape.

Step 2: The Mold

Picture of The Mold

The first step in carving the shark fin is to make a mold for the spray foam. This is a pretty crude process, so the mold can be pretty crude. The basic goal is to minimize wasted foam, so just an outline of the base of the fin will suffice. I lined the mold in plastic wrap to act as mold release.

Step 3: Spray

Picture of Spray

This part is pretty simple. All you need to do is fill the mold with expanding spray foam. Remember, the expanding foam expands, so you won't need quite as much as you might think.

Note: I tried to use styrofoam the first version of this boat, but the epoxy I used for the fiberglassing melted the whole thing. Remember, to test your material combinations before going forward with a build.

Step 4: Carve

Picture of Carve

The shark fin will probably look more like a giant shoe than anything remotely resembling a marine animal, so there's a significant amount of shaping to be done. Start with a hand saw and carve the hulking mass of foam into a rough shark fin shape. Next, use a rasp and sand paper to refine the shape to something you are satisfied with.

Step 5: Fiberglass

Picture of Fiberglass

Fiberglass is great. It is a great way to put a hard shell foam models. If the object you are fiberglassing is really important I suggest using marine epoxy and marine grade fiberglass. If it's just a shark fin prank you are working on, the inexpensive stuff you can get at Home Depot or Lowe's will do just fine.

Before you begin, remove the boat's lid (with the shark fin attached) from the rest of the boat.

Start by cutting the fiberglass so that it drapes reasonably well over the shark fin. Next, mix up your epoxy and drizzle it over the entire shark fin, and smooth it in over the whole fin.

Step 6: Sand

Picture of Sand

Fiberglassing results in a less than perfect surface finish, so significant sanding is usually necessary. An orbital sander with two or three progressive grits will be sufficient to do all of the sanding.

Step 7: Paint

Picture of Paint

At last it is spray paint time. It turns out Montana makes a paint color called 'Shark', so I can't help but recommend that particular color. I'm not sure how accurate the hue actually is, but it must be close enough. I suppose any shade of grey will probably do just fine though (actual shark color may vary).

Step 8: Scare

Picture of Scare

Now it's time to scare your friends in the water. The boat probably won't move as quickly or steer as well as it did before the fin addition, but if your experience is anything like mine, it should work pretty well.

I recommend being careful about your location of choice. Creating a large amount of panic is probably not a good idea.


R3D-000 (author)2016-03-29

Cool. Looks like fun

tezza the terra (author)2015-07-27

Did this come from Mick Fannings Shark in South Africa?

Nope, I didn't even know about that.

TvoAqui (author)2015-07-22

Looks like fun.

rob21a (author)2015-07-20

That's hillarius

Aleator777 (author)2015-07-08

RC Shark Fin lives at last! V2 w/ lasers yes?

CobyUnger (author)Aleator7772015-07-10

Oh for sure!

bravoechonovember1 (author)2015-07-07

this is so cool!

any good reactions? :)

The park rangers passing by got a good laugh during the filming. Nobody was truly scared by it yet.


CandyLove11 (author)2015-07-07

Lol we live in a lake I'm gonna do this and prank my little brother! Thanks for sharing

CobyUnger (author)CandyLove112015-07-07


M3G (author)2015-07-06

Haha this is awesome!

CobyUnger (author)M3G2015-07-07

Oh thanks, I am a big fan of your pranks too.

gravityisweak (author)2015-07-06

Haha! This is excellent! It reminds me a lot of this one.

CobyUnger (author)gravityisweak2015-07-07

The kayak trailer is amazing. Well played.

aleff (author)2015-07-06

may be in a pool... but at the sea?? not a joke!!

CobyUnger (author)aleff2015-07-07

How about in a lake or bay or lagoon?

mart33n33 (author)2015-07-06

Surf's up in Aquatic Park! ;)

CobyUnger (author)mart33n332015-07-07

Gnarly waves braaaahhhh...

About This Instructable




Bio: I build, I teach, I learn. Happiest when covered in saw dust, sweat and machine grease. Visit for more projects and info.
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