All the complicated nuances of 'tidal bore' are not, actually, going to be conveyed into Esta's brain by a cute little 2nd-circle spell. Maybe you get that off 4th-circle Tongues but you do not get it off Comprehend Languages.
Esta has grasped that the canyon is about to flood. He has not grasped the part of the compound Baseline word that invokes a mathematical concept about how compressing a passage increases the speed, amplitude, and kinetic energy of fluids traversing it.
Spells which are not part of the standard Worldwound loadout: Water Breathing (3rd-circle for both clerics and wizards, 2 hours / caster level).
Items which are not part of the standard Worldwound loadout: Necklace of Adaptation (list price 9000gp, albeit in a price catalogue that is less than totally 100% trustworthy about what things would cost if you were not buying them from that particular merchant network).
ESta's Bag does have an emergency Air Bubble scroll, but it'll last, like, literally 1 minute. It is an incredibly cheap-ass 1st-circle scroll that you carry because "it costs only 25gp", not because it is part of a clever advance strategy that requires you have an Air Bubble lasting 3 minutes instead.
Still, that ought to be enough to swim to the surface if this canyon floods...? Timing the cast might be hard, though. He thinks those time units sounded like "less than (somewhere around 2 minutes)" but Comprehend Languages is not really gonna do precise math for you.
Esta will give himself a 3-minute Bull's Strength, which is going to take him another 6 seconds after he pulls that cheapass scroll, so he can swim while in armor. And then, sure, start trying to clamber up the least steep ascent he can find, with his augmented strength. That'll save him some effort on swimming to the surface later.