There is no exact number, and you don't have to sink all the ships, only Captain Crawfish's ship. You need to buy a Phoenix Warbird to sink it.
There are many museums in poptropica like in mytholygy island and many more island's!
There are many islands of poptropica
Many, many, many people have. Including myself. Except for I am about to start working on Shrink Ray Island. But other than that Island I am done with Poptropica.
9 ships.
Five
9 ships.
9 ships.
9 islands
one.
There are animals on many Poptropica islands. There is a Safari on Nabooti Island, cryptids on Cryptids Island, and in several quests. See the related questions.
five gems
There are five jewels missing