Do I need to take it slow?

No, swimming isn't like running - there's no 10% increase in distance per week rule. You're free to swim any distance you can swim as long you're listening to your body while you swim and know when it's tme to stop or at least switch up what you're doing. For example, if your calves start cramping, put on a pull buoy and do some pulls to give your legs a rest; if your shoulder starts hurting, grab a kickboard and do some kicks to give your arms a break. If you start cramping AND your shoulder starts hurting then that's a good indication you're done for the day. However, straight distance swim workouts aren't the most beneficial workouts when it comes to building endurance, at least not if that's all you do. In this respect, swimming IS like running - swimmers do tempo workouts, sprint workouts, and distance workouts just like runners do because we build up our endurance and become faster the same way as runners. And our idea of hill training is swimming with a drag chute (just so you know).

And our idea of hill training is swimming with a drag chute (just so you know). My pool is uphill heading out of the deep end and downhill heading the other way. Sometimes feels like uphill both ways.:D

The answer is also a bit age dependent. If you're in your teens or 20s, there would be few limits other than listening to your body. As you move to middle age and older, be more cautious. I've had to learn this lesson the very hard way... And by the way, that 10% per week "rule" is bogus. It is WAY too aggressive of a growth pattern. Jack Daniels, the long time, decorated running coach (not the whiskey), has some excellent books and articles about safely growing run distance. Its much more conservative than the absurd 10% per week stuff. Good luck.

Can you find a masters team? Ask some swimmers or a coach to give you workouts that might help in stroke mechanics.

You are correct in drawing a parallel between running and swimming. In fact, you should ease into any sport when you are first starting out. Swimming-wise, there are a few specific reasons you should start slowly. First, although swimming is a low-impact sport, it is not an injury-free sport. The most common injuries occur to the shoulders, and the vast majority of these injuries are caused by improper stroke technique. Swimming is a highly technical sport, and developing the proper technique - especially when you are first starting out - is an absolute priority to avoid potential injuries. Doing too much too soon can also lead to injuries, which is another reason you want to take things step-by-step. Even if you do "listen to your body", you should still not be swimming for as long as you can non-stop. This is because another key to successful swimming is developing your efficiency in the water. In order to build up efficiency, you can't practice mindless swimming. The workout needs to be divided into drills, kicking sets and swim (interval) sets to maximize your full potential and develop symmetry and an equal amount of strength throughout your entire body. How the workout will be devised is best left to a coach who has seen you swimming and who is a specialist in technique - not simply someone writing up standardized workouts that are not geared towards your individual needs. Your comment about focusing on high elbows and feeling shoulder pain illustrates this point perfectly. We can't see ourselves in the water - we need a coach (with specific expertise) to be on deck watching us swim and knowing exactly what we need to do to improve efficiency and avoid injuries. When my swimmers see their video analysis for the first time, they are often surprised to see that their perception of how they swim differs from how they *actually* swim. My suggestion to you is to get a coach who will be able to analyze your technique and work with you on developing it. Good luck!

I ask because up until really just now I was just swimming "naturally," i.e. not focusing on technique. Last week I tried to focus on high elbows and it seemed to make my shoulders hurt.

I agree 100% with Julia. I'm off swimming for at least another week, possibly more, because of a neck and shoulder injury that could have been caused by overuse, or could be something else like arthritis. I did a measly 30 laps a couple weeks ago after having lifted weights (not shoulder sets) at the gym, and now I'm back in physical therapy. If I could afford a private swim coach, I'd get one. Although my technique isn't bad and when I'm swimming freestyle I do not feel any discomfort, the aftermath has been painful. I cry when I read about how others are doing miles in open water, and now I can't even swim a couple of laps. Boo, hiss. So take it easy, get a coach, and build slowly because no matter how enthusiastic you are, no matter how good you feel in the water, you can suffer overuse injuries if you are not careful.