Amphibious NPC Sylvan Hounds, But Not Player?
Canines are amphibious I thought, and Sylvan Hounds count as amphibious so I woulda thought they did…
But if that’s so then I’d just guess it’s a mechanical decision. ArenaNet had to limit the options for underwater content in a balanced way. While highly annoying and sometimes nonsensical (why do engineers get to core elites underwater while necromancers – and probably other professions – get one core elite?), it makes sense… I guess? Meh, underwater balance doesn’t make sense.
But the tl;dr of it: mechanic reasons, not lore.
Wait for the underwater combat overhaul many want even if they don’t realize it… the one that’ll likely never happen… for that to match lore.
Stop treating GW2 as a single story. Each Season and expansion should be their own story.
I don’t think the choice of which skills to make available underwater was ever made for balance reasons (although they made sure every profession had at least one full bar), but on the basis of what skills were easy to convert to underwater. The skills of the canine family are based on leaps and howls: they probably felt that the combat style of the canine family wasn’t something that could be easily converted to underwater combat.
People don’t hate Scarlet like Game of Thrones fans hate Joffrey.
They hate her the way Star Wars fans hate Jar Jar Binks.
Moas can also "walk" underwater aka have an underwater animation, but they are still no amphibious pets.