Open water track, is this normal?

Sometimes yes. Other days it’s better. What was the distance you swam? Despite the track I usually see some difference in the distance swam from that recorded around 5% give or take.

Measured on Google taking a reference point I took when I was swimming in straight line: 1100meters. GC show 1350mts

Ideally you'd have an accurately measured distance but that's not always possible of course so hard to say whether your GC distance is grossly out, unreasonably out or ok. Few of us are able to swim in a dead straight line so estimated distances from a map could be off by a reasonable amount too. My swim distance over the 2000m buoyed course can vary by 200m or more depending on where I start/stop the watch, whether the tide is in or out, and whether I can see where I'm heading due to waves etc but it usually is less than 10%. Here's some examples from swims earlier in the year with my 5+:

A good track - that was me swimming off course as the sea was rough and hard to see sighting points

then this...which was pretty ordinary - extended swim an extra 500m (or should have been). And it wasn't me swimming all over the place either lol!

then back to being reasonable again

But going back to December (found this while looking for something else) it was diabolical...

Zip up the original .fit file for the activity and the GarminDevice.xml file you'll find in the Garmin directory on the watch and send it to the outdoor beta team at this address - [email protected]. Tell them exactly what you experienced and make sure you include details of the expected swim distance covered for reference.

You might not get a reply immediately but if you keep getting the same result and keep sending them the files you might eventually. You could also try Garmin Support through the usual support channels.

I recently compare the open water activity with a colleague with a Fenix 5 non plus, and after the activity he get a completly straight line while me is still a zig zag line. Which could be the problem?

I’d question his completely straight line. How did the distance compare? Would you post images?

Yes here u have

This one is with fenix 5s non plus

That’s actually a fantastic reading! From my experience, the fenix 5x plus is good for around 1500-2000 yards and then it begins to go bonkers.

This swim was today, but it was really around 2,000 yards. 
the one from May 30th last though was pretty good. The watch started to go nuts a couple times but overall did what it was supposed to.

 Garmin has been no help regarding this.

i had the same problem With my fenix 3hr.

it continues to count as if your moving when you are not.

 You can swim an extra 500 yards from resting 30 a minute. 

That's terrible. Last time I swam with my 5+ it was nowhere near that bad. 

it continues to count as if your moving when you are not.

That will happen if the last GPS signal was some distance from where you've stopped. The watch will 'correct' it's position and draw a straight line. I have a 9s 250m as a result!

Contact Garmin Support but also see what happens next time you swim. Hopefully a one-off. Usual questions though:

How was it in the past - not just last swim but the swims from last season?

Has your swim stroke changed?

What GPS setting?

Smart or 1s recording? Better with 1s.

The 5+ has had challenges in the open water but when I last swam with mine it seemed to have improved as you can see from some pictures I've posted. But then sometimes it goes and throws a wobbly.