https://community.usms.org/swimming/f/general/26738/cooldowns-should-be-several-hundred-meters-at-leastThe Science Of Swimming Faster book makes a strong case for "long cooldowns", at 55-65% of your max speed. The writers argue for 25-35min of easy swimming after a short race, or an intense speed session, and 15-20min of easy swimming after a longeren-USTelligent Community 12