The parts of the body that Aquarius rules are the calves and ankles. Let me explain, in Astrology each sign is aligned with or has some kind of affinity to a body part; rules, as we say, that body part. In some way it symbolizes what the sign is about. Aquarius is a sign of great exploration and loves mental and physical exploration. The calves and ankles propel us forward, so in many ways it symbolizes the Aquarian experience.
Sexually this part of the body is also very sensitive and is open to erotic touches, nibbles, and kisses. You will find, if you are in bed with an Aquarian, a very good way to start the sexual experience is to just lightly touch the back of the calves down to the ankles.
Here's a place where the Aquarian not only becomes aroused easily, but then, in terms of a sexual position itself, sometimes Aquarians really enjoy making love standing up because this way you can entwine your legs around the Aquarians and these parts of the Aquarian body are touched and brought to greater sexual ecstasy.