Bluetooth, by nature is a short range wireless communication technology. With larger devices, the internal antenna is longer and the operation range is often better. Small earbuds like the Apico work best with the phone/source device at 5-8m and in line-of-sight.
Bluetooth does not transmit through water. To avoid cross-body interference from the water in our bodies, please try to locate the earbud and your phone as below.
Please also try to avoid interference from other sources: