"switch to the other tank and exit."

Yes that is my choice also (independent backmount).


But assuming full gas loss of both (manifolded) tanks - right at thirds in both directions - and facing an air sharing exit... In a hypothetical situation where there isn't enough extra efficiency to squeeze out of the dive then there is likely no way the two divers can share air to either of the planned exits. Lost all gas on one diver - unless weighted properly for zero gas in tanks many divers in that situation would be buoyant. They barely made it from either direction when swimming each separate and weighted normally - now floating, excited, tied together with a 7' hose, and already "past thirds" by a bit. ---- Then Olsen would be the best choice.

If Olsen wasn't an option divers would be depending on flow, efficiency and luck to make it to Peacock by either route. But once past the cookie - and thirds - continuing in the planned direction to the exit would be the default (shouldn't require discussion). Pot Hole is a terrible option for trying to surface but maybe their best hope. Maybe better handholds for pull-and-glide on the Pot-hole line for a more gas efficient exit than pure swimming... but with both divers tied together "extra efficiency" is a vain hope at best.

Being weighted properly would obviously be a good idea. I think both "buoyant Out-of-Air diver" situations I'm thinking of were with Aluminum tanks - steel tanks less of a problem for most. But with Aluminum tanks actually wearing enough lead to be neutral with empty tanks would actually be important in that situation.

Sidemount or independents offers additional redundancy vs the "Completely out of air" situation. The "Completely out of air" with a manifold situation is pretty unlikely anyway. Sidemount or independents you'd have to postulate both regulators failing simultaneously - and even then you can still get to the gas.


If the system were significantly deeper then deco gas might become an issue. Olsen might get one alive to an exit but with insufficient gas remaining to complete deco. Bent would be better than dead - but if the gas situation were less obviously dismal to reach the original planned exit(s) taking a chance on the farther exit starts looking more attractive.