View Full Version : Converting Lap times to Open Water

Bill M.
October 31st, 2003, 11:51 PM
I have never swam in an open water event. I started swimming again in january in a 25 meter pool. I can comfortable swim 1500 meters in 24 minutes (no flip turns). Realizing open water has tides/currents etc. I am attempting to calculate what I might be able to swim a mile in open water. Any thoughts? Also, how many meters should I be training on a weekly basis to swim 4.4 miles. I am 46. Thanks..

November 1st, 2003, 06:54 PM
Well Bill,
I'm not much help but hey its A reply! I think its much more a matter of swimming with good form as long as you can without stopping in the pool also build up the distance and time slowly and steadily. I haven't found pool swimming to convert to ocean swimming in terms of meters/miles at all. Try to get out in the ocean from time to time and see how long a mile takes, compare that to what you are doing in the pool.
Tides and currents will dramatically alter your speed as will wind, surf and swell. So I'd predict how long you think you'll swim and try to swim that long-in time in the pool. Now my advice is from the stand-point of an endurance swimmer who competes only against herself and the elements and who looks for speed so she can go further.

I was swimming @ 2-2.5 mi/hr in an out and back course, I did a 3 miles swim with the prevailing currents in under 1 hour so even comparing day to day its hard to predict. Recently I completed a 6mi swim in under 3 hours but 2 dyas later the 1 mi swim with strong swell took nearly 40 minutes.

Rob Copeland
November 3rd, 2003, 08:32 AM

In addition to tides, currents, wind, waves your open water time is effected by how straight you navigate and how efficiently you site the course. Some veteran open water swimmers will swim nearly as fast in open water as they do in pools, maybe 2 to 4% slower. Newer open water swimmers typically break stroke to site and donít always maintain a straight course, both of these will add to time to the swim, maybe as much as 20 to 30%.

It sounds like you are getting ready for the Chesapeake Bay Bridge swim. If it is are you planning on wearing a wetsuit? And you wear a wetsuit, you need to practice in it to see where you chafe, and make sure to use BodyGlide or similar stuff to prevent chafing.

As for workouts, if your goal is to complete the swim, I would suggest swimming at least 3 to 4 times per week with one of those a long workout, around 6,000 to 8,000 yards. If you are not able to go that far, yet, then work your way up to it.

Also, I would suggest that as soon as weather permits; get in one workout per week in open water. I know a few people who can swim for miles in a pool (with open turns or flip turns) and find it difficult to complete a mile in open water. The little rest at each turn does make a noticeable difference.

Good Luck

November 4th, 2003, 02:30 PM

I was asking the same question last spring when I signed up for my first open water swim. Unfortunately the answer "it doesn't convert" is accurate.

My first swim was a one mile cable swim, 2 laps of a 1/4 mile long cable. The water was pretty flat, almost no wind and no currents. However I swam at least 20% slower due to the grouped start and problems sighting.

The grouped start was interesting as everyone starts off in a quasi-sprint for the first 100 meters or so, I saw this happening in earlier heats and told myself I wouldn't participate - that I was here to "complete", not "compete". But let me tell you when folks are flying past you, you get caught up in it and before I knew it I was swimming WAY too fast for my cadence and breathing.

The second problem was sighting. I didn't think this would be any problem since I wear perscription goggles and breath every three stokes (alternating sides). I figured I'd get a view to each side and be able to keep straight as an arrow.....HARDLY. Being use to swimming in a pool; I didn't take into account the abstruction even small swell can have on sighting. Secondly, sighting straight out to the sides isn't worth a crud because you really can't tell when you get off course, unless you're WAY off course. I thought I'd be able to judge if I was drifting to one side or the other, but I couldn't. Go stand in the middle of a big parking lot; look to each side....then move 10 feet to one side or the other and look to the sides again....you can't tell you've moved - same problem I had in the water. So I had to breast stroke a couple times to get re-oriented. The other disorienting feature is the dark water, when you're head is down you have absolutely no frame of reference, I didn't realize how nice that black line on the bottom of the pool was until I was in water so dark I couldn't see my outstretched hands.

I eventually figured out that I could sight if I brought my head up at a 45 degree angle, instead of 90 degrees to the side, as I took a breath. I now practice this when I lap swim by "sighting" on the corners of the pool.

For your first open water swim I'd suggest you be able to swim twice the distance of the event you enter....but just for the first one. I entered the mile swim even though I swim 2 miles a day, knowing I could swim twice the distance really helped me deal with all the new things I encountered and not having to worry about swimming the actual distance was reassuring.

I hope your swim goes well.


P.S. I finished 2nd to the LAST in my event, my two elementary school age boys met me on the dock screaming and yelling. The crowd was cheering - it was FANTASTIC.

September 16th, 2004, 11:11 AM
Hi Bill,

by now You must have already succeeded in the Chesapeake Bay Race but since I just joined this forum and discovered this thread today I would like to add my 2 cents, because I think this is a good question many beginners will be concerned about.

There are three reasons why You are slower in open water:
1. navigation: There is no black line on the bottom, this has been mentioned already in previous posts. On top of that, sighting where to go next takes additional time. At least it is slowing down, because as soon as the head goes up, the feet go down, increasing drag.

2. No pushing off the edges: It takes me 30 seconds less on a short course pool completing 1 km compared to a long course pool (when I do 20 turns less). With every good push off the wall in a streamlined position I will gain my own body length plus an extra 3-4 meters. So for every km in open water I am "loosing" 20-40 good push offs.

2. The edges of a pool are beveled, the cables between the lanes have spiral-shape, the water surface of a pool is smooth, three reasons for less drag!

3. waves, wind, currents and tides. On the average these forces should compensate each other, ie it will always take the same time for every 100 miles You swim, but there can be great differences between one swim today and the next one tomorrow.

4. cold water may cause the muscles to work harder.

Timing myself on average it takes me about 10% longer in open water to complete a mile or a kilometer. But I haven't swum in really rough waters yet ...


September 21st, 2004, 11:17 AM
I swam a ten mile race in Lake Ontario at Confederation Park Hamilton Ontario Canada. It was a half mile course. It took 7 mins. for the with the wind section and 14 mins against the wind, Other factors were the waves and the cold water (51 degrees f). 40 of the top marathon swimmers in the world started the race only seven finished. I finished second and received $3500. for the effort. Pool swimming can help with the conditioning, however you cannot compare the two.

George Park www.swimdownhill.com

September 22nd, 2004, 05:08 AM
I agree that it is not possible to compare lap-swimming times with open water swimming times. There are too many factors involved, especially currents, wind and navigation.

I swim in 2 3KM races this summer in 56 and 58 minutes. Then I did a crossing of the Strait of Messina, which is 3.3KMs. This was NOT a race, just a crossing, and since I had 2 paraplegic friends in the group, I started out swimming with them. I swam on my back a lot to see the view of Sicily fading away in the distance, and did some breast stroke to see the coast of Calabria approaching (it's a GORGEOUS swim!) Even though I took my time, the swim took only 45 minutes thanks to favorable currents, and experienced boat pilots (one boat is required per swimmer by law) who navigated us wonderfully! Even the slowest swimmers made it within one hour.

Speaking with a disabled swimmer friend of mine this weekend at the race in Lerici, he told me that he did a 2-way crossing of the Strait 2 years ago. It took him 36 minutes one-way, and an hour and 41 minutes for the return. Does that tell you something?

Have fun!

September 22nd, 2004, 01:49 PM
Other than favorable currents, most of the open water impacts have been negative on time as compared to lap swimming.

Wouldn't the buoyancy of salt water (assuming ocean/bay, not freshwater lake) be a positive factor?

September 23rd, 2004, 03:43 AM
Other than favorable currents, most of the open water impacts have been negative on time as compared to lap swimming ...

agree - if those impacts cancel each other out between start and finish You may still be slower by 10% compared to lap swimming, I would guess.

Wouldn't the buoyancy of salt water (assuming ocean/bay, not freshwater lake) be a positive factor? ...

Definitely! As an avid freediver I could write stories about bouyancy. Salt water has a specific weight of 1,03 on the average. According to the Archimedes principle an immersed body is 30g (approx. 1 ounce) lighter for each liter of water it displaces. We are talking about 2 Kilos (4 lbs) less weight in salt water with average salinity. Besides: the surface of the ocean seems to be more penetrable compared to a lake surface. May be, because of it's unique undulation.

Quoting jdut: ... I have read (maybe in Penny Dean's book?) that salt water feels about 5 degrees warmer at the same temperature reading ...

Is anybody supporting this theory? I would be grateful for Your answers


Sabretooth Tiger
September 23rd, 2004, 12:27 PM
Nothing I can proffer on a scientific basis . . . but I've surfed in 55 degree water in Southern California and Riverboarded (aka "hydrospeed") in 55 degree freshwater in the American River . . . the American River feels bone chillingly colder at 55 compared to the Pacific. Absolutely no doubt based on my personal experience that freshwater feels much colder.

For what my 2 cents is worth,


September 24th, 2004, 09:09 AM
@Carl - thanks a lot!

To redirect this thread to it's origin: converting Lap times to Open Water I would like to add my 2 cents worth of experience: Even though I am slower in open water it is less tiring. Almost a contradiction! I find it much easier to swim 5 K in the ocean as compared to 5 K in a pool, even though I would do them faster in a pool. It takes a much stronger mental effort to pace an olympic size pool 100 times up and down, compared to swimming (a relatively) straight 5K-line in open water. I think nothing compares to swimming in the ocean. Trying to be in harmony with the waves and "feeling" my way through them is so much more exciting! As the ocean is alive and always moving I feel like constantly drawing new energy from the water that keeps me going much further than in a pool.

By the way, it is very difficult to get a free lane in an Austrian swimming pool as a lap swimmer, which makes things even harder.

September 24th, 2004, 10:37 AM
I love swimming in rivers. The river I like best is the Bostonnais river in La Tuque Quebec. I used to swim from a friends backyard on the river. We would swim up to the waterfall about three miles out of the current and swim back in the full current. We sometimes had to dodge the logs coming down the river but what wonderfull things we saw.