Swimming lenght not accurate at all

Now I´m a bit confused again about this: The distance shows right at first like today 550 metres, then it simply stops counting and even though I swam another 100 metres is still stayed at 550. It has done this now every time but a bit different meters. Why??

Normally, all problems come from the user (not the tool or machine).
When you swim, do you get out of the wall normally? I.e. by pushing the wall? If you just start slowly, the swimming watch might not start  counting. 

Read CAREFULLY the user manual.

Sometimes, when I’m doing drills it does not count or count in double…it’s The way it is…

But This is a watch for swimmers. And it is great for swimmers.

The same for me here, i did 2000 meters and swim2 gave me 3900 meters.
Swimming pool lenght has been setup to 25meters and i swim regularly, but not for the watch.
I did a repetition of 100m breakstroke, 50m crawl with long push at the beginning of each 25m (advices i read in the doc).
Might me a good idea to insert a min/max time per length into settings or other to help the algorythm's lenght counter.
At least a min time per lenght so the watch does not display impossible result, like 10 sec for 25 meters or 3.9m per stroke (3100m/807 strokes), in my case this result is impossible ^.
Don't think it is impossible to achieve this in the code.
I just bought this watch to count my lenght, to free my mind and it was my first try today, I may have missed something in the settings.
I think they should focus on what the result/performance looks like, i mean, even if i make stupid stroke for 3 sec, the system does not record 25meters/1lenght in my case depsite of sensors/...
It will be the first thing i will put in an algorythm for this kind of watch --> consistent results.

Well, what can I say(?), it works. For almost all (real) swimmers. 
Is it perfect? Nope. There are no such machines…specially when most of the errors come from the user…

I use Garmins in the pool for ages and they are not worse, on the contrary. There are no major flaws in the algorithms. But if we stop or change style in the middle of the pool, have terrible technique, or whatever, the watch cannot compensate, of course.

Well, Caleb DresselI made 20,16 at 50m, so for sure he can do 25 meters in less than 10 sec…
;)

Okay, I paid attention to doing what you said in the pool, stopped, glided and made hand movements more like swimming and strong. It worked. BUT.. I don´t understand the calories. I ordered the HRM but I haven´t got it yet. When running outside calories are reasonable, why swimming ever harder an hour it shows like 91 calories? What makes this clock think that swimming don´t spend calories?? My heartrate was like 120 many times I watched during swimming and still calories didn´t go up reasonably. That should haven been more like 500 calories. Any ideas about that?

I do not have any knowledge on that matter.
As I said, please read the user manual. In any case, Garmin says it all: https://support.garmin.com/en-US/?faq=u2osOnTW2x7prnX2hnRst6 
Also, about HRM: support.garmin.com/.../

I made some progress about accuracy with training program.

My training program (swimming pool lenght 25m):

1)Lap Button Press to start
2) make 100m breaststroke
3) make 50m freestyle
4) loop 5 times
5)Lap Button Press to stop
total 750 meters.

1st try: 625 meters on the watch
2nd try: 725 meters on the watch
3rd try: 700 meters on the watch
not too bad.
let focus on the 625 :


I press lap button - bottom right and start swimming breakstroke after a long push
1st 25 meters for the watch (1.1 on the image):
1mn 50sec --> pbl

2nd 25 meter for the watch(1.2 on the image) counted as the 4th for me:
32.8 sec

Is there a way to say to the program/algorythm what my average is ? or to help it understanding a turn/lenght
so the watch understand/record this:
1.1 breakstroke
1.2 breakstroke
1.3 breakstroke
1.4 breakstroke

1.5 freestyle
1.6 freestyle

1.7 breakstroke
1.8 breakstroke
1.9 breakstroke
1.10 breakstroke

1.11 freestyle
1.12 freestyle
etc

I dont understand why it is so difficult to put such parameter in the watch algorythm.
Alogythm is not even based on stroke to calculate a lenght ?

It is calculated, i think,i might be wrong, on a particular movement u have to do at the end of the lenght to count it as a lenght.

Adding a min and max time for a lenght might help a lot for accuracy.
so i dont make 25meters in 1nm 50 or 3900 meters in 45mn(see my 1st post)when i did only 2000 meters.

Because this clock is clearly made for swimming and competitions and not for the waterrunning I bought another clock (Suunto spartan sport) and it works perfectly for waterrunning. Anyway these instructions here were essential for it to count pool lenghts right :)