HTing something in water
 

I was trying to test XP on blue just now and my troll SK was meleeing a rat in some water, and when I tried to HT it said that my spell was interrupted and it used the cooldown on HT even though the HT never went off on the rat.

I assume this is because of how water line of sights spellcasts or something?

Working as intended.

You must be in the same fluid medium as your target to land a spell. Otherwise the spell will go through, use mana and recharge time, and not hit or stick on your target.