Well, that's up to you, but what it really means is the you can't push any of the buttons while in water as they are not sealed. People have been know to accidently hit the buttons while swimming and had moisture creep in, but for the most part, as long as you don't hit the buttons and change you battery gasket once a year (comes with the battery kit), you should be fine.
I personally don't like the
Yachtsman leather
band for use in water, and
Suunto does not currently make a replacement
band for that, but I've seen some after market that fit.
Hope that helps,