Thank you for reaching out to us.
Based on your description, it would be permissible to immerse in the early morning of the eighth day. It would be preferable not to see your husband altogether during the day, though we understand that might not be feasible. You should take special care, however, to avoid yichud with your husband between the immersion and the following nightfall. This may take some advanced planning.
Please see our detailed page on immersion in a natural body of water
here and please let us know if we can be of further assistance.