It seems that you're using an outdated browser. Some things may not work as they should (or don't work at all).
We suggest you upgrade newer and better browser like: Chrome, Firefox, Internet Explorer or Opera

So, after fighting zombie dragon and changing to Piranha-Man I went to the volcano where I found a changing platform (where you change to Mouse-Man and get the Thunder Ring). There I changed to mouse-man, and kept it since I wanted to know what secret treasures might be in the town's tower.

Now, I can't find a way to change back to Piranha-Man.
I can't get back to the volcano platform, as that would require Piranha man to get above an underwater obstacle.
Seems the zombie Dragon is gome for good, so I can't let them curse me into Piranha-Man again.

I guess the next path would be to get into the underwater shipwreck, but I can't get there until I can swim around obstacles.

Can anybody recommend a place to go next?
I've tried opening the passage below the tower with the Thunder Ring bat that's awfully hard o_0'
This question / problem has been solved by dtgreeneimage
Since you have the Thunder Ring:

On the way to the beach, there is a block you can break. Breaking it will reveal a question mark, and collecting it will reveal a door that will take you to a transformation room, which will allow you to change back into a piranha. (Note: If you happen to have the Magical Sabre, make sure to switch to a different weapon when trying to break blocks.)

(As a side note, if you didn't have the Thunder ring, you would be stuck on earlier versions of the game; on newer versions, the game will automatically turn you back into a piranha so you can go back to where the Thunder Ring is.)
Wooho :D Thank you. I've never looked in this direction.
Thank you!

[edit: since I've run past it at least three time, here's a screenshot for others that might hit the same problem]
Post edited February 18, 2018 by gdkags