Or rather his 'stealth' power says "FROM THE DEPTHS: Aqualad can use Charge. When Aqualad occupies water terrain, any line of fire drawn to him is treated as if it crosses blocking terrain."
Does this mean I can never perplex/prob them?

Can I choose not to use it when I use perplex/prob?

Powers are not optional, if he is in water lines of fire are blocked, your turn and opposing characters turn.