During niddah, a couple should refrain from going on a pleasure trip/activity together as well as avoid light-headed behavior together.

Wearing a modest bathing suit, of the type that covers as much as generally worn clothing, does address the issue of appropriate attire in front of your husband. However, the issue of a joint pleasurable activity also needs to be addressed. If your intention is to swim laps in the same pool, it seems to be permissible as long as you take care to maintain enough distance to avoid physical contact. It would also be fine for the two of you to take your children swimming. If you plan on going swimming to have fun in the pool together/splash each other/joke around, etc. it should be avoided while you are niddah.

Please feel free to get back to us with any further questions.