Talk to me about IM swim training

Do as much as you can in the time available.  What more can you do?  If you have the time, though, there is no reason to be limited to an hour when doing the workout (even if that's what the plan says).

Most of my swims were roughly in the one hour ballpark (rarely less, sometimes a little longer).  This had more to do with my schedule than the optimal way to train.  If I had extra time, I would usually just swim a little more.  If I had to get out early, I would try to cut the cool-down first, then the drills, then any other warm-up.  I'd always try to do the main set.

I would only do an extra run/ride if I had the time and felt like I could handle it without impacting the rest of my workouts.  Generally, though, I would rather sleep more if I couldn't swim than add a run/ride.  Rest is valuable too.

I can add a couple responses...

I basically average 2:00/100 for a workout (including rest, kick sets, drill, etc).  That's how I schedule my swims.  However, I have a lane to myself all the time.

If it were ME training, I would shoot for the distance, no matter how long it takes, to be honest.  You have to get used to swimming that 2.4 miles.

I would say MOST of my swims were around 3000-3500, and it would take me anywhere from 55-70 minutes.  During my peak weeks, I had to get several in the 4000-4500 range.  So around 90min pool time.  Those made for some long days in the pool.

If you can't make a swim, I would probably forget it (or reduce it) and not bike or run instead.  If you do run or bike, I would probably make it a recovery run/ride as to not overtrain in those areas.

Swim was my stong suit, and I subscribe to the idea that the stronger swimmer you are, the better your IM day will be.  I strove to get out of the water fast and feeling as if I hadn't yet done anything.  That put me ahead of the large pack of people and set the pace for a good day.

My swims were 3K on the short side, 5000 on the long (which were pretty few). 

As for time, get in what you can.  Honestly though, doing drills in IM meat training is pointless to me.  During early base?  sure, but if you are in the thick of training, I don't think drills do anything for your swim (my own personal opinion).  Some things you can control.  Try to get there on time.  And levaing early?  what is that?    Some things you can't, working late, pool hours, etc.  Control what you can, let go of what you can't

My longest swim was about 1:20 or so.

I wouldn't make up "swim" time with bike/run, they don't translate.

That's odd.  I've been to dozens of pools in my time and never found a pool like that.

Can you swim twice in a day to get a longer distance day in?

I'd do what I could given time limits but for me being a slow swimmer I'd be in a pickle as I'd only be well under 3000 yds in the 55 or 60 minutes they give you.

Maybe find a different pool you can do a longer swim once a week or when weather warms up do longer swims outside in open water.

What I'd watch in how long you are able to swim and be sure as you get closer to your IM you are getting some swims in that are in the 3500+ range on a regular basis. For me the difference between a 3000 and 4200 yd swim was big and I needed my body to handle the swim as well as possible. 

When I started run/bike tapering I actually increased my swim frequency and distance so I was swimming last 3 weeks 5x a week. It worked great as ows take time to drive to and from lake or pond, meeting up with a friend to swim and chatting afterwards...ultimate diversion for me while tapering.

The swim is my strong suit and the longest swim I had pre race was 3500 yds. And I only had maybe 4-6 of those. And I broke my collar bone 12 weeks prior and for 7 of those 12 weeks I had to swim using only one arm and kicking.

That being said, my swim goal prior to breaking my collar bone was to do the swim in around 1:10. I ended up at 1:18, but hey, with my shoulder still hurting I was happy at that point.

My point is this. Longest swim was 3500 yds, and for 7 of the 12 weeks prior to the race I really couldn't get in a thorough workout at all, and my time didn't suffer all that much.

YMMV

Mirrored goggles and you can ignore 5 minutes of stink-eye   In my case, I'd just start breathing on the opposite side as the hour closes in. 

My swims are on the order of 2:00/100 and my longest planned swim is 4500 yards (BT-Intermediate) so I figure about 90 minutes.  Straight through, I can do 4200 in about 1:18-1:20

I'm with Akidoman, you're a strong swimmer, and you've got the technique down.  just work on the distance - which you say is not a problem.  The bottom line is that you've got to get the 2.4 miles done easily so you are fresh for the rest of the race.

I'm also a fairly stong swimmer, and that's the part of the training plan that I dropped when things got complicated.  I ended up missing quite a few of the swim workouts.  I did however get the long ones in and concentrated on swimming long rather than trying to improve my speed.    I concentrated on gliding between strokes, and resting and sighting strategies.  With your speed you'll be ahead of most of the pack anyway.

So, I'd drop the drills and just swim.

you should tell them that you are training for an IM and you are a Very Important Person !!