Thanks for all the advice!
I was of the lanes' etiquette as I have been swimming in pools all my life :) and yes perhaps 2 people is not that busy!
I'm probably spolied now to be in a country where swimming poools are so common, not so long ago while in London it was almost impossible to swim as pools are few and overcrowded.
After today's practice I still noticed that I tend to bump into the lane dividers.
It's probably because before TI, I used to swim close to those dividers to give me some visual feedback on my speed and flow.
I'll try to be more in centre of the lane from now on, probably it's also a useful excercise to improve your balance while skating.
all the best from here