The Philippines are tropical and hence are home to just about every tropical disease with the traveler’s name written on it. Bear in mind the usual ways to avoid getting diarrhea though and you should be okay – just make sure you stick to bottled water unless you can find a good well.
The Philippines are a step up from places like Cambodia or Laos but often their attempts to ape western standards go horribly wrong – like the toilets with broken flush mechanisms…
The real dangers for the traveler are in the Filipino cities where crime and violence are a given. You don’t want to be wandering around after night away from people and bright lights. Foreigners are a clear cut target here as muggers suspect (with reason) that you’re probably carrying more money than the average victim and you don’t know your way around.
Still, the main cause of deaths amongst travelers is almost certainly on the roads and Filipino drivers are as reckless as anywhere. When going anywhere by jeepney, try to find an older driver – he probably doesn’t watch as many Hollywood movies and besides, he hasn’t died so far.
Ferries sink frequently but there’s nothing you can do to avoid this beyond burning a candle to your favourite saint once in a while. You could carry a life jacket with you but you’d look ridiculous.
In the event that a boat goes down, the Filipinos have a strict procedure that every passenger will be expected to follow. It’s called “every man for himself.