The Ironborn have CPR down well so being drowned is not that dangerous. Being drowned then ressuscitated is not nearly as dangerous as going on raids.
On a related note, how would you guys like ASOIAF to end? I want Dany to die, Jon to become the King in the North, and Victarion to become the King of the Iron Islands. I would like Westeros to become several independent states again, and the Ironborn to be a major power. But I don't think any of those are going to happen, based on GRRM's writing style.