Yes, sharing lanes is absolutely normal. At times at my pool, you can wait a LONG time if you want a lane on your own, and pool rules dictate that you share if all lanes are occupied. The only way to get a solo lane is to show up at odd hours, like mid-morning on a Sunday or after 8 on a weeknight. Frankly, there is a hell of a lot more room sharing lanes in a pool than there is for most mass-start Ironman swims, so think of it as good practice.

The sharing etiquette where I swim is to get the swimmer's attention, either by standing at the end of the lane or (better) sitting with your legs in the water, then both swimmers are expected to communicate how they want to share (circling or picking a side. Most just pick sides).

While open water swimming with a wetsuit is something you should also be doing, I think time in the pool allows you to be more focused on things like form, drills, speed, etc. Plus, if you really are uncomfortable swimming, I don't see how going out in a lake is the better choice right away. And yes, there will be the occasional little kid who is faster than you. Deal with it.

1) Sharing lanes is for real

No one at your local pool will be surprised if you ask to join them in their lane ... and you shouldn't be surprised if someone jumps in with you. Read more here if you like. Swim teams and some masters groups will routinely swim with 5 or 6 to a lane.

2) Masters classes are are not only for serious swimmers

Re: Masters groups, I have a bit of a cautionary opion originally posted a few weeks ago in Masters Group and Being a Newbie and slightly edited:

In my experience with the masters teams in my area, a 2:12 per 100m slow pace is, uhm, just getting in the way. Masters swimming is different than cycling clubs or running groups. You get off pace in a run or ride and the group easily moves past and you just fall back. But in a lane (a shared lane with 4-6 per lane is possible), if you're off pace you bog down everyone else. Imagine doing speed work on a track and walkers and stollers and dogs on leashes take up all the lanes. You'd be cheesed too. It could be like being a new cyclist and showing up at an office park crit with USCF Cat IVs and IIIs: a big ol' wreck.

I could be wrong, I don't know your masters team (nor do I know your pace). But my local masters teams are mostly former D-1 swimmers and people who only swim and compete nationally for masters titles. I tried training with them, and even though I've finished an IM swim in 1:12, I was proverbially blown out of the water. Go watch a class first. Sit on the pool deck, tell the coach you are interested in joining, and sit back and watch the churn. If the masters team is big enough, they will double (triple, quad, etc) each lane and if you can't hold someone else's pace, you'll clog up the whole workout. Some lanes will be for 1:00 per 100, some lanes will be slower, but not much. (An example might be a 500m in 7:30 warm up). And if you stop during a set and hold onto the wall, you may get feet to the chest during a flip-turn/push-off. Also, the stroke may be an issue. Many of the drills alternate strokes, and if your free is 2:12 slow, then learning a fly or breast stroke (disclaimer: I can do neither) may be prohibitive (not to mention pointless for a tri), then you may be the only person doing free-only.

Keep in mind the coach probably won't tell you this or kick you out because s/he wants your money, but just go and watch (bring your stop watch) and see if any lanes have people in your pace lane. I think another option to explore - if you want a swim group to train with - might be to find a tri group.

there is a lifeguard at my gym, but he was late one morning. The pool lights were out, and the swimmers were waiting patiently outside the door. One VERY old, cranky lady, (with a flowered bathing cap) was having NONE of that, and opened the door and hopped in the pool to do her exercises...in the pitch black darkness. I wouldn't recommend that. But it was the story of the week at the J.

If you find a Master's class, you can always call and find out if it would be a fit for you or not. If it doesn't fit you right now, maybe they have some suggestions.

I'm not in New England so I don't know if you have a YMCA near by but you should definetly check it out. Depending on the time of day at our Y will depend on the size of the lane but they are all always shared. In the morning, when they first open (5:30), they have broken up in to three sections. A fast lane, medium lane, and a slow lane. There is a wide range of swimming abilities. The lanes are really wide so passing is very easy but I have been there when the lanes are narrower and the passing is a little more difficult if it is crowded. They split the lanes up by times. If you can swim down and back in under a minute then you are in the fast lane. If it takes you a minute to 1:30 minutes to swim down and back you go to the medium lane and any longer time you go to the slow lane. (it is something along those time lines.)

More times than not, I'm the slower one in the fast lane. One guy that swims, use to be pro-triathlete, one swam in college. There was another girl in the lane that was a swimmer in college. Another guy that is just simply stronger than I, but I can't move down because some that are in the middle lane should probably be in the slow lane and are too proud to move there. I am use to the fact that compared to them I am slower but I also try and use them as my training aids. If I have to do sprints - I try and take off right after them and stay on their feet.

Good Luck! I hope you find somewhere soon!

+1 to the etiquette advice; and be prepared if others do not observe the same rules. i've crashed into people who just jumped in front of me or the group of foreign exchange students who were just playing in the shallow end of the lap lanes.

but don't sweat it either way. i'm really really really bad in the water, but i can swim back and forth. and i'm usually the slowest, but sometimes i'm not. either way, i'm in the pool. and if the swim is your weak spot, it doesn't matter how you do it, you HAVE to put the time in the pool if you don't want to freak and feel like you're dying the whole swim...
....ask me how i know.

You should consider yourself EXTREMELY lucky that you need only worry about sharing a lane with ONE person. I train @ my local NYSC, and sometimes I'm lucky enough to share a lane with one person, but most of the time I'll have to decide between swimming with two other people much slower than I, or just postponing my workout because I wouldn't be able to complete a beneficial workout swimming between those two.
Sometimes this raises my ire to the point where I'd like to casually tell the people swimming 1:30 LAPS (and stopping for another minute @ the wall), that they're simply wasting their time, because the 10 calories they burn doing their workout could easily be accomplished by walking 2 laps around the pool.
Then I remember my swim etiquette, and the fact that other swimmers have just as much right to swim in the lane as I do. I swallow my anger and pray that my quiet perservance will be rewarded by another swimmer's early exit.
***IT COULD ALWAYS BE WORSE***

I've actually had a woman leave a lane to share with someone else when she saw me coming. I sort of took offense and told her I would be happy to share. She said I scare her because I am too fast. SCARE her! Another time, another lady said I could share her lane, but said, "Please don't hurt me." I am NOT kidding. and I don't flail- I stay on my half the lane. I don't know if I should be proud or embarrassed about my reputation in the pool :S

Well onto the subject of timing. I swim normally at lunch, and will punch in from 30 to 45 mins on my workouts. I tried getting up earlier but i ran into all the interlopers who were working out and had to share lanes.

At lunch except for the months of Jan. and April I get to pick which empty lane to get into. Now Jan. an April (why no clue) I have to share lanes for the first couple of weeks. Then the hippo's go back to grazing in the peepee (wading) pool at my local YMCA.

Perhaps the best two-sided advice out there. Kat nailed it. At the end of the of the day, an IM swim is nothing but a big-ass washing machine*. The swim in a local pool with a few people sharing lanes doesn't even qualify for floating in a bathrub status in comparison.

*Eventually it calms down...like when you get out of the water.