Is this wise?
Probably not if it were a 'real' one. It was included in a parcel from t'other side of the werld from a friend's husband. He has a bizarre sense of humour and this would seem to be a popular "toy" down under. I will see if I can find a linky.
You're lucky I didn't call him Snoopy 
My kids have had similar ... a few days in water and some sort of rubber creature hatches then expands in the water. They shrink if taken out of water and allowed to dry out and can be "grown" again by re-immersion..... Oh have I ruined your surprise .....
Top Tip: Don't read this post to the end.