As has been noted, not the most fun experience, deathly boring and doesn't feel natural either as you aren't actually moving through the water.
Getting this post back up! I've been thinking about making some sort of setup for my pool I have at home (I own a gym/spa) which is 20x10 metres which is plenty enough to swim in but I've got the feeling it lacks distance for some intervals. I'm an okay swimmer (under 30' in HIM) and when I get to a 50m pool or open water I lack the upper body strength to endure those distances. I'm trying to qualify for the WC 70.3 next year in beginning of may in Aix 'd Provence which is pretty early so Its hard to get some open water sessions in and 50m pools aren't open here in The Netherlands.
TLDR: Is it beneficial to get a Swim Tether of some sort so I can train 'longer distances' so to say. In my 20m pool I most times just get to swim 12m due to pushing off etc. Or is it not that great and say just swim more in a 20m pool?