All Dolphins around disappear but one in Spectator.

Cannot reproduce. Was the world created in an older version/snapshot?

Relates to MC-130455.

I was with another player when I went.

In a server, LAN world...? Your description does not give helpful information!

Yes in a LAN world.

Still cannot reproduce. Was the world created in an older version?

By the way, I'm not a Mojira Staff but I'd suggest you to change the description, here's an example:

The bug

While I was playing with a friend in a LAN World I used the command /gamemode spectator. I was in an Ocean ruin, with dolphins, but when I used that command all the dolphins disappeared.

How to reproduce

1. Spawn or find a group of dolphins.

2. Set your gamemode to spectator by using /gamemode spectator.

All the dolphins will disappear.