"I can change Melby, but it would take 1 hour and 10 minutes. I don't think we have the time" says Bellamy

“And she’s not up for a quick swim? It’s more so we can be sure we dive into the correct hole. If we have to climb back up because it’s the wrong way it will be hell.”

"No swimming for Melby. Before I jump I will recall her into a pocket dimension so I can call on her again when we are out of the water." says Bellamy

While the others discuss, Zane has already given one end of his 50 feet of rope to Jarsali and has thrown the rest of it over the railing.

"I have to be first - it was my idea."

He then does a motion with his hands and mouths a little something, and disappears from sight (casting invisibility on himself).

Out of nothing, you hear, "Oh, please tie another 50 feet of rope to it, just in case. When you feel it slacken and pulled twice, then you know it's safe to take this way down."

And he climbs over the side to start lowering himself into the whirlpool. It's possible that at one point, some muttering can be heard, "This is scary as f... man up... you got this..."

Nodding determinedly, Rel taps invisible Zane on the shoulder (after a few tries) just before he descends, granting him her father's divine Guidance.

She makes eye contact with where she thinks the tabaxi bard's face is earnestly.  "We think very differently, you and I, but I have faith in you.  Go well."

Jarsali grabs hold and commands a three of the Zhelezo to take the rope "I am not much for holding things taught. Let the brutes take care of that work.." As she passes the rope, the three Zhelezo grab hold as Zane has already jumped from the ledge and into the water. 

Zane, the swirling vortex of water spins you about as you are siphoned into the whirlpool. You can easily tell that any chance to escape it at this point would be for nothing as you cling to your rope. Suddenly, a final pull into the hole of the river bed consumes you. You feel the need to fight for air but suddenly, the water gives and falls to the open spaces below as you dangle from a rope above a familiar area, the same area you described the directions to, so very precisely and meticulously to Jarsali.

Zane, make a perception check!

(Also, your ridiculous survival roll got you here. Jarsali would have only known the long route if it weren't for that roll.)

Perception roll for Zane: 14 total (used Guidance as well).

He's breathing heavily, trying to quiet down his pounding heart.

"What we had to give him is a sending stone. Now we do not know whether he is alive and went scouting or is dead and needs some help." Lana sighed. "Oh well. Let me be next. If I am fine down there, I'll let Jarsali know through the sending stone."

Just in case, another 50' rope was added to the already existing and Lana dived after Zane. Should everything go smoothly, she will send Jarsali a message, pointing out where and how it would be better to jump for the others ((can it be counted as Help?))

“But he said he’d pull on the rope twice to send the signal that it’s save, shouldn’t we wait a moment?” Asks Tex.

Zane, as you dangle from the rope, you look down and notice there are four individuals standing at attention while the woman that the group has begun to fear, the woman dressed in violet and gold, addresses them. With the noise of the waterfall you are unable to hear exactly what she is saying but you are able to make out a few words here and there, "Trust nobody" and "Kill on sight". She then moves on down the eastern passage and the "guards" spread out to watch several areas. (I will post a map later on when I am home)

As you continue to dangle, the rope begins to slowly lower you down when suddenly, your new tiefling friend comes rushing through the waters and slides down the rope, resting just above you.

(So far they have not noticed you though I do need a stealth check while the rope continues to descend seeing as the others holding the rope are continuing to lower you until they receive the signal)

Lana (silently cursing her impatience and unjustified worrisomeness) does her best to dangle quietly and preferably in the water. (Stealth 20)

If given the chance, Rel would have given each descending person Guidance (as described in post 1404).

Guidance can only be active (concentration) on one person at a time, and Zane already used his (post 1413), but it should still be active for Lana, who began her descent just afterwards (post 1414). 

(Would gladly use it to add to the Stealth: +2)

Zane stealth roll (not using advantage, I don't remember if/how invisibility gave it or not): 13

(How far is the end of the rope from the floor? Is there some room behind the waterfall? What do the guards look like? Are they sword/shield or bows or seemingly unarmed?)

(Initial idea, if unnoticed, is for Zane to lower himself all the way down and drag the end of the rope behind the waterfall so that anyone lowering themselves down would be at least somewhat hidden by it)

Zane

Rel, Bellamy and Tex, You continue to watch from above as the Zhelezo lower the rope, now with two of your companions in the water, seemingly disappeared into the whirlpool. Jarsali says "This is giving me a bad feeling, but I think we need to stand our ground and wait for a signal. The line is still taught it seems so I would assume the others are still OK"

"I am willing to wait. The signal will come. I believe in Zane and Lana" says Bellamy

“So do I,” agrees Tex. “Both of them are able scouts and Lana even has the sending stone in case they are in a really tight spot.”