1. Generated a world without strictures (via server.properties)
2. Fed the dolphin a fish
3. Server times out and crashes as it endlessly searches

[05:12:25] [Spigot Watchdog Thread/ERROR]: ------------------------------
[05:12:25] [Spigot Watchdog Thread/ERROR]: The server has stopped responding! This is (probably) not a Spigot bug.
[05:12:25] [Spigot Watchdog Thread/ERROR]: If you see a plugin in the Server thread dump below, then please report it to that author
[05:12:25] [Spigot Watchdog Thread/ERROR]: Especially if it looks like HTTP or MySQL operations are occurring
[05:12:25] [Spigot Watchdog Thread/ERROR]: If you see a world save or edit, then it means you did far more than your server can handle at once
[05:12:25] [Spigot Watchdog Thread/ERROR]: If this is the case, consider increasing timeout-time in spigot.yml but note that this will replace the crash with LARGE lag spikes
[05:12:25] [Spigot Watchdog Thread/ERROR]: If you are unsure or still think this is a Spigot bug, please report to https://www.spigotmc.org/
[05:12:25] [Spigot Watchdog Thread/ERROR]: Be sure to include ALL relevant console errors and Minecraft crash reports
[05:12:25] [Spigot Watchdog Thread/ERROR]: Spigot version: git-Spigot-492a779-731e819 (MC: 1.15.1)
[05:12:25] [Spigot Watchdog Thread/ERROR]: ------------------------------
[05:12:25] [Spigot Watchdog Thread/ERROR]: Server thread dump (Look for plugins here before reporting to Spigot!):
[05:12:25] [Spigot Watchdog Thread/ERROR]: ------------------------------
[05:12:25] [Spigot Watchdog Thread/ERROR]: Current Thread: Server thread
[05:12:25] [Spigot Watchdog Thread/ERROR]: PID: 22 | Suspended: false | Native: false | State: WAITING
[05:12:25] [Spigot Watchdog Thread/ERROR]: Stack:
[05:12:25] [Spigot Watchdog Thread/ERROR]: sun.misc.Unsafe.park(Native Method)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.concurrent.locks.LockSupport.park(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.concurrent.CompletableFuture$Signaller.block(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.concurrent.ForkJoinPool.managedBlock(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.concurrent.CompletableFuture.waitingGet(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.concurrent.CompletableFuture.join(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.IOWorker.a(SourceFile:93)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.IChunkLoader.read(IChunkLoader.java:89)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.PlayerChunkMap.readChunkData(PlayerChunkMap.java:825)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.PlayerChunkMap.lambda$21(PlayerChunkMap.java:481)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.PlayerChunkMap$$Lambda$2874/1116854850.get(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.concurrent.CompletableFuture$AsyncSupply.run(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.IAsyncTaskHandler.executeTask(SourceFile:144)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.IAsyncTaskHandler.executeNext(SourceFile:118)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.ChunkProviderServer$a.executeNext(ChunkProviderServer.java:567)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.IAsyncTaskHandler.awaitTasks(SourceFile:127)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.ChunkProviderServer.getChunkAt(ChunkProviderServer.java:104)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.World.getChunkAt(World.java:198)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.IWorldReader.getChunkAt(SourceFile:108)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.StructureGenerator.getNearestGeneratedFeature(StructureGenerator.java:111)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.ChunkGenerator.findNearestMapFeature(ChunkGenerator.java:69)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.WorldServer.a(WorldServer.java:1420)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.EntityDolphin$b.c(EntityDolphin.java:347)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.PathfinderGoalWrapped.c(SourceFile:41)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.PathfinderGoalSelector.a(SourceFile:75)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.PathfinderGoalSelector$$Lambda$3064/1587583737.accept(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.stream.ForEachOps$ForEachOp$OfRef.accept(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.stream.ReferencePipeline$2$1.accept(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.stream.ReferencePipeline$2$1.accept(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.stream.ReferencePipeline$2$1.accept(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.stream.ReferencePipeline$2$1.accept(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.Iterator.forEachRemaining(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.Spliterators$IteratorSpliterator.forEachRemaining(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.stream.AbstractPipeline.copyInto(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.stream.AbstractPipeline.wrapAndCopyInto(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.stream.ForEachOps$ForEachOp.evaluateSequential(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.stream.AbstractPipeline.evaluate(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.util.stream.ReferencePipeline.forEach(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.PathfinderGoalSelector.doTick(SourceFile:69)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.EntityInsentient.doTick(EntityInsentient.java:655)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.EntityLiving.movementTick(EntityLiving.java:2519)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.EntityInsentient.movementTick(EntityInsentient.java:504)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.EntityLiving.tick(EntityLiving.java:2351)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.EntityInsentient.tick(EntityInsentient.java:273)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.EntityDolphin.tick(EntityDolphin.java:198)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.WorldServer.entityJoinedWorld(WorldServer.java:623)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.WorldServer$$Lambda$3044/838382792.accept(Unknown Source)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.World.a(World.java:718)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.WorldServer.doTick(WorldServer.java:395)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.MinecraftServer.b(MinecraftServer.java:1076)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.DedicatedServer.b(DedicatedServer.java:393)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.MinecraftServer.a(MinecraftServer.java:978)
[05:12:25] [Spigot Watchdog Thread/ERROR]: net.minecraft.server.v1_15_R1.MinecraftServer.run(MinecraftServer.java:823)
[05:12:25] [Spigot Watchdog Thread/ERROR]: java.lang.Thread.run(Unknown Source)