Simple Instructions:

Before install, make sure to delete the previous version! For the best results!

Install the Addon,

Add it to your Minecraft world,

When in your Minecraft world,

Get this items: Cod, Salmon, Tropical Fish, Pufferfish, Kelp, Sea Pickle,

(Disclaimer: I use ocean related items, because I also work on a super cool dolphin related addon! It's much easier for me using those type of items!)

Look straight up to enable Acrobatic properties (Ninja jumps/elegant slow amplified jumps (If those don't work, you have to disable them first, then enable again!)) and straight down to disable them,

When enabled: Select one of the items: Cod=Backflip, Salmon=Frontflip, Tropical Fish=Sideflip, Pufferfish=Double Frontflip, Kelp=Double Backflip, Sea Pickle=Mixflip

Then Crouch Jump or Sprint Jump to trigger the Animation!

The animations are dynamic, those can be used in multiple ways!

Make sure to use Third Person view, to enjoy this amazing animations in Singleplayer!

This addon should be Multiplayer proof!

Enjoy the show!

New Features!!!:

You now get text info for what you can do holding and using different items!

Camera Shortcut:

It's way better to be in Third person view to watch your amazing moves! There's a shortcut for this now: Get a Target block, hold it, look up to go in Third person and watch your epic stunts! Look down holding this item to go back in First person! This makes it way more convenient for mobile users!
 

Body Dynamics:

Now there are 3 dynamic ways to move your player body and steer in mid air while performing tricks! There are unlimited ways to use this, even some crazy odd ones! Use your imagination for this! Get: Iron ingot, gold ingot, copper ingot and emerald to start using this features! Hold one of the 3 ingots to switch between 3 different dynamics! After holding one for a short time, you will be able steer mid air doing some crazy stuff! If you don't like this effects or just want to move normal: Hold a emerald to undo the effects! Disclaimer: This effects are for entertainment and might not always be realistic! Although with proper use of imagination those could actually be used in a realistic way though!

Freerunning modes:

There now is a more subtle way of freerunning that fits more with the actual sport: Get a diamond, redstone dust and lapis lazuli to start using this feature! First make sure you got the right jump properties! Look straight down to disable the ninja jump, if you used any ocean related item jump before! Now just start your parkour adventure, as now you get a little jump boost while sprinting! You will lose the boost, if you stop sprinting for a brief moment! If you jump high enough, you automatically randomly do a acrobatic trick based on the item you holding:

Diamond = Frontflip based basic freerunning,

Redstone dust = Backflip based basic freerunning,

Lapis lazuli = Sideflip based basic freerunning.
 

Fence hopping:

When you are close to any type of fence, you get a nice little jump boost! If you jump over the fence with this effect, you can do cool random tricks! This add some variety as normal jumps have a set trick!
 

Wall climbing:

With the addon installation, there now is a extra behavior pack featuring a epic experimental climbing system! I recommended you give it a try! If you enable it, you will be able to climb against any flat wall just by timed jumping! This mechanic allows you to do many cool wall related tricks aswell! it's even animated! Just play along with this amazing mechanic! It's super versatile! Known issue: Sometimes you could clip though corners using this! You could easily prevent this by using this function carefully! It really adds up to your imagination!

New videos:

Older videos:

Screenshots: