Swimming by numbers

Almost nothing. My hair is barely wet
yet. But hey, I’ve got to ten per cent
already! Ah the freedom! Keep on
forward and then I’ve swum a fifth
then this one makes a quarter.
The water’s warm, the sun is shining
– it’s crazy to be counting in this heaven.
At this rate I’ll be finished really soon.
And now I’m feeling loose, benign,
(it’s often like that when I’m halfway).
Well… even so it’s easy to lose count
but it doesn't really matter
and now I’m very near two-thirds.
(For goodness sake, just enjoy the swim.)
Ah three-quarters. I’m moving
through the water well today.
Just two to go when this pair’s over
And here’s the second of the pair.
So this should almost be the last
but when the trees, the sky, the sun… I do not want to stop.
On days like this the numbers should not count
but I can't stop and now my careful fractions
and percentages are out – ooh look, a prime!
and now a lot of factors, that feels good.
A quarter of a century – too easy – look
at the shadows (an alphabet) on the
changing rooms (and cubes of three)
a lunar cycle and now here comes
a bigger, better prime. OK,
one kilometre – now I’ll have a shower.

Riddle - how long is one length?


*************

Hidden numbers:

Almost nothing(1). My hair is barely wet
yet. But hey, I’ve got to (2) ten per cent
already! Ah the free(3)dom! Keep on
for(4)ward and then I’ve swum a fifth
then this one makes a quarter.
The water’s warm, the sun is shining
– it’s crazy to be counting in this heaven(7).
At this rate(8) I’ll be finished really soon.
And now I’m feeling loose, benign(9),
(it’s often(10) like that when I’m halfway).
Well… even(11) so it’s easy to lose count
but it doesn(12)'t really matter
and now I’m very near two-thirds.
(For goodness sake, just enjoy the swim.)
Ah three-quarters. I’m moving
through the water well today.
Just two to go when this pair’s over
And here’s the second of the pair.
So this should almost be the last
but when the(20) trees, the sky, the sun… I do not want to stop.
On days like this the numbers should not count
but I can't stop and now my careful fractions
and percentages are out – ooh look, a prime!
and now a lot of factors, that feels good.
A quarter of a century(25) – too easy – look
at the shadows (an alphabet) (26) on the
changing rooms (and cubes of three) (27)
a lunar cycle(28) and now here comes
a bigger, better prime (29). OK,
one kilometre – now I’ll have a shower.

Each line is one length. There are 30 which makes a kilometre so each length is 33.33m long, as noted/challenged by Philiphoto