If troops are submerged should they become webbed when attacked by Arachnaean Weaver? Or does submerged only protect against physical damage against all troops, and not status affects against all troops?
“Submerged troops avoid all damage effects from spells that are targeted at the whole team (e.g. “all troops” or “split randomly amongst”).”
So status effects or anything that is not split damage or damage to all (or any of its many synonyms hidden in the game 
) will still apply to Submerged troops.