I keep thinking that I'm headed out of here soon, so I'm not looking for my dream bike. I want something that will give me the greatest efficiency for longer distances on the road. I'm looking at 25 mi (50 rt) rides for swim laps).

A bike for this season, maybe next. I have to be aware of the enticement factor as well because I anticipate the bike to be locked in public for significant periods(6-8 hrs on campus). Ultimately, I am serious about training for an Ironman. The budget has identified a few bikes; should I opt for a lower ended newer bike like a Denali, an older Schwinn, or a Trek 700 hybrid for durability? These are what I have access to at this point.

Thanks for opinions.

Here's the gear of the 2013 Kona winner. If you can make it fit, it'll probably be the most efficient thing you can ride. Here's the rest of the winner's gear:
2013 Kona Top 15 Men Bike - Slowtwitch.com


1. Frederik Van Lierde
Belgium
height: 184 cm / 6 ft 0.5 in
weight: 72 kg / 158.5 lbs
bike time: 4:25:35
bike frame: Cervelo P5
size: 54
aerobars: 3T Aduro
front wheel: Mavic CXR 80 T
rear wheel: Mavic CXR 80 T
tires: Mavic Yksion CXR, Power link (back) and grip link (front)
components: Shimano Dura-Ace D-2 (11sp)
gearing: 54/44 Osymetric and 11/28
powermeter: SRM
display: SRM Powercontrol 7
saddle: Prologo Nago Evo Tri CPC
helmet: Ekoi CXR13
pedals: Mavic
cycling shoes: Mavic Tri Helium
clothing: Castelli
sun glasses: Oakley

I suspect the only thing I could afford there are the glasses.

I prefer road bikes for distance for the drop bars alone and the varying hand positions. Find a decent used road bike that fits. It will get stolen, so maybe buy 2 at a time ?

Okay. If I understand your question, stay away from the Denali.
If both the Schwinn and the Trek fit you, get the lighter of the two.
If not, get the one that fits.
If neither fit, look for one that does.
Fit trumps just about everything when cycling distance.

What's your budget - bike plus everything else?

A vintage road bike could be an option. A Trek, Schwinn, Miyata road bike from the '80's would suit your needs. $200 would get you a very nice used bike. Where are you located? And what size bike do you need? Or your height?

Get a used Centurion Dave Scott Ironman model. That fits. You know, 'cause it says ironman right on it.

Go for the Schwinn. I wouldn't guess the Denali would last long unless you're really lucky. I've owned an old Schwinn and a Trek hybrid and the Schwinn will be better for long road rides. My Schwinn Sprint weighed 28 pounds but in college I could keep up with people on much better bikes.

Cheapest POS that still rolls. should be able to find something around campus for less than $50. Bikes get stolen daily at colleges. No lock is going to stop it. Only defense is being surrounded by other bikes that are bigger targets, and spending as little as possible.

Then get a used older steel road bike with drop bars, and put on clip on aero bars for your triathlon training.

https://columbus.craigslist.org/bik/4400000132.html

Le Tour De France Road Bike 22"

This... buy two bikes. Get your budget, then buy a bike worth that much minus $100. Spend that $100* on a beater bike that you don't mind if it gets stolen.


Note *: Please adjust this dollar amount to fit your current economic status. I wouldn't gripe about replacing a $100 bike, but that might not be your case since you're in college and are probably living off Ramen**.

Note **: I've always found that making dumplings*** with Ramen takes the whole meal to the next level.

Note ***: Not those damn Jewel / Kroger / Target dumplings either. Go to Chinatown****.

Note ****: I live in Chicago, so Chinatown is an option for me. This might not be true for you.

If you never ride off road there's no reason to compromise ride quality on pavement. So get a proper road bike with 700c wheels and 23-25mm tires, caliper brakes, and drop bars. New or used, it'll ride better than any mountain bike or hybrid with slicks on pavement.

Yep. During law school I rode a baby-poop brown Sears Free Spirit 3-speed ladies with a big ol' wire basket on the front. Perfect campus bike.

baby-poop comes in all skittles colors, brown is not as interesting as the blue/green.

I ate a bunch of beets one time. Things got kinda crazy.

Get an old cruiser for campus use, reconsider your other budget options. On Ironman, by the time you pay entry fees, travel costs, bike shipping costs, motels, wetsuit, etc., the bike could be the small end of your expenses.

If you want to train for the an Ironman (I assume it's a smaller local one, but either way the answer is the same), I would buy a bike that will put you in the same riding position you'd be riding for the Ironman. A road bike with...aero bars? Your body will adjust to whatever bike your'e riding the most, so I wouldn't suggest a hybrid. 50 miles round trip would also benefit from a road bike.

An older Schwinn vs a newer Denali would be a dilema. Either one should be fine. Biggest thing would probably be trying to figure out what bikes would allow aerobars - I've read that some are much better for that than others.