Re: Apollo 13 astronauts and space suits

Your question was quite difficult for me to track down as you can find lots of conflicting 
information on the web and NASA press kits.  Anyway, I finally decided to ask Dr. David Akin, my 
former Advisor at the University of Maryland Space System Lab for some insight.  So, my answer 
is largely taken from his knowledge.

The crew of the Apollo spacecraft were required to wear their suits during all critical mission 
phases in case there was a leak in the spacecraft.  Such phases were: launch, docking, 
spacewalks, etc., including landing.

So, in general, the suits/helmets were worn during landing.  Once in the water, the recovery 
divers would open the hatch in the top of the module and throw in a special biological isolation 
garment that the crew would change into.  As you might guess, the Apollo modules were very 
cramped and this was a difficult task at best.  Not to mention the spacecraft was bobbing in the 
ocean!

During Apollo 13, the crew had been through so much and were in questionable physical 
condition, they didn't want to make the crew have to do yet another time-consuming or 
physically demanding task.  Also, they never landed on the moon, so there was no need for the 
isolation garment.  So, for that landing, they did not wear the suits.

After Apollo 14, it was decided that there was no risk of bringing back any "moon bugs" so they 
did away with the biological isolation garments.  It is possible that in the later Apollo missions 
a reentry in shirtsleeves was "okayed" by NASA, but I do not know and I can't find any 
information that indicates it was.

I hope this answers your question - it certainly was fun trying to dig it out for you!

-Steve