This paper presents an investigation on a potential biomedical RFID planar coil operating at 13.56 MHz for measuring the blood pressure level, mounted inside an abdominal aortic aneurysm. The results show that a wireless communication is achieved in a perimeter of 60 cm, while respecting the ISO 15693 standard for vicinity contactless cards. Measurement and electromagnetic simulation results show that the inductive coupling is deteriorating if the planar coil is in direct contact with water without correctly encapsulating this coil. An electric model is given for our proposed RFID planar coil immersed in water.