Illaoi's position can be seen in the Fog of War.
Illaoi's tentacles have 2 states: active, and dormant. Active tentacles stand tall, have 2 hitpoints, can be used to hit enemies with, and only stay active when Illaoi is nearby. Dormant tentacles shrivel up, have 1 hit point, and turn into this state when Illaoi leaves the area. The issue with this is that the enemy team can see the current state of tentacles even in the Fog of War. They can even see when tentacles spawn in the Fog of War. This is kind of a big oversight by Riot, but I have some solutions.
I propose that when Illaoi is NOT visible, all tentacles should all appear to look dormant to Illaoi's enemies, until they either: (1) swing at you, or (2) you auto attack them, revealing if they are active or dormant, or (3) Illaoi becomes visible, revealing all tentacle states globally at that moment. Just to clarify, Illaoi's tentacles would look exactly the same to her own team as they do now, so it wouldn't give away where the enemy team's wards were.
Additionally, if a tentacle has NOT swung at anyone in its lifetime and has also NOT been seen by the enemy team at any point with actual vision then it should NOT be visible to the enemy team until it does. Think Rek'Sai tunnels for this one. You can't see them when they spawn, but as soon as you do see them, they stay visible. (But the state of the tentacles would remain a mystery as soon as you couldn't see them anymore.)
Finally, the ways that tentacles spawn. There is Illaoi's passive spawning them, and then there are vessels that spawn them. I think that when Illaoi's passive spawns a tentacle, it should NOT be visible until it is seen or it swings at somebody, because it gives away her position. However, when a vessel spawns a tentacle, I am totally fine with the tentacle being instantly visible, as long as after they swing at you, they appear to look dormant again if Illaoi is not visible, even if Illaoi is nearby. Just to clarify again, Illaoi's tentacles would look exactly the same to her own team as they do now, so it wouldn't give away where the enemy team's wards were.