It’s more than mild, but Dolphins aren’t as effected, iirc. It’s pufferfish which has a toxin that can kill humans. While it’s possible to touch and be safe because our skin will block it, small scrapes or accidentally getting it in our mouth or eyes etc could be incredibly dangerous, where as dolphins use their snouts and mouths and seem to get just a bit high.

Edit: also it’s in some dispute whether it was intentionally getting high or just accidental poisoning.