I need help with this riddle

Here
We are brave pirates always riding the sea. We are less than one hundred but as tough as can be. We sleep in three bunks on top of each other. Our numbers double from one bunk to another. We dance in joy all through the night. In groups of fives under the moonlight. But 12 of us were swallowed by waves. Leaving alive more than two thirds of the braves. Still we continue our journey refusing to fail. So tell me how many of us are left to sail?
Please help