Fish Simulator

Fish Simulator lets players turn into a fish and swim around as one. You steer it with your normal movement keys and mouse, you breathe underwater, and everyone else just sees a cod with your name over it. Or without your name, if you would rather troll.
The catch: your real body stays on land where you left it. In survival it can still be hit, and if it dies, so do you.
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Features
Turn into a fish. /fishsim become spawns a cod at your feet and puts you in it. Salmon, tropical fish and pufferfish work too, and you can add squid, dolphins, axolotls or any other water mob in the config.
Real control. You are not stuck spectating. The fish goes where you go and looks where you look. You shrink down to fish size so you fit through the same gaps, and Dolphin's Grace keeps you quick.
Breathe underwater. Your air never runs out while you are a fish. Your fish can still dry out on land though, just like a vanilla fish (you can turn that off).
Your body stays behind. A mannequin with your skin, your name and your gear stands where you left. Survival players take every hit to it out of their real health, and get a warning on screen. If the body dies, you are yanked back and die right there, with the right death message and your items dropped at the body.
Hide your name. /fishsim nametag takes your name off the fish. Now you are just a cod. Nobody suspects the cod.
Admin fish menu. /fishsim admin lists every fish within 10 blocks, closest first, with distance and position. Click one and you are in it. Already a fish? Click another and hop across. Your body stays where you first left it.
Safe to use. Fish players cannot break blocks, open chests, pick things up or attack. Bodies and spawned fish are never saved into your world, and if the server crashes mid swim, players are put back to normal on their next join.
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Commands

• /fishsim become [type]: turn into a fish
• /fishsim leave: go back to your body
• /fishsim nametag: hide or show your name above your fish
• /fishsim admin: open the fish menu (admins)
• /fishsim list: see who is a fish right now (admins)
• /fishsim reload: reload the config (admins)

Aliases: /fsim, /fishsimulator
Permissions

• fishsim.become: use /fishsim become (everyone by default)
• fishsim.nametag: use /fishsim nametag (everyone by default)
• fishsim.admin: admin menu, list and reload (ops by default)

/fishsim leave needs no permission, so nobody gets stuck as a fish.
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Config

• Which fish players can become, and how small they get as each one
• The admin menu search radius (10 blocks by default)
• Whether players need to be in water to become a fish
• Fish drying out on land, on or off
• Dolphin's Grace, on or off
• Name tags shown or hidden by default, and what they say
• The "Gone fishing" text under the body
• Every message

Requirements

• Spigot 26.3
• Java 21 or newer
• No dependencies

Paper is not supported yet.
Install
Drop the jar into plugins/ and restart. That is it. Hop in some water and run /fishsim become.