Agree with the things said, assume everything will bite or sting in the sea to be safe. I have been nailed by a titan triggerfish 3 times, one in which physically made me leave the water when snorkelling and watched me in the shallows until i had left then on re entry it came flying back - they are insane in nesting season!! When muck diving, and taking photo's, if u kneel down just fan the sand a bit, as stonefish, demon stingers etc.. are hard to see. I have friends in boracay who know people stung by scorpionfish and its not very nice at all!! Also i heard about one guy who was snorkelling and 'something' released a toxin cloud in the water and caused severe skin reactions and now his leg is completely scarred (have seen the leg) - no idea what creature did that!!!
Box jellies which i believe can be found in philippines are fairly uncommon unless you get far south. Blue ringed octopuses are deadly but unless you touch one you are unlikely to get bitten. I think also the pfeiffers flambouyant cuttlefish actually can bite and contains the same tetrodatoxin as the blue ringed octopus!!
take care with any octopus, titan tirgger, scorpionfish, lionfish (which can be aggressive if too close), demon stingers, stonefish,hydroids, fire corals, mantis shrimps, urchins, cone shells (textile!), striped catfish, some hairy sea slugs, sea snakes (though generally not aggressive), stingrays (see steve irwin), jellies, waspfish etc....