Based on a interferometric optical fiber hydrophone, a fiber Bragg grating (FBG) hydrophone towed array with a diameter of 20 mm is realized. This single-fiber hydrophone array without splices is realized by using the multi-wavelength FBG continuous writing technique. The average acoustic pressure sensitivity of a hydrophone unit is -143.9 dB, and the fluctuation of sensitivity is limited within 3 dB. To suppress the crosstalk in the FBG hydrophone array, weak-reflectivity FBGs are utilized,reducing the crosstalk to 53 dB. Moreover, polarization-induced fading is eliminated by three-channel polarization diversity receiving. A 32-element FBG hydrophone towed array with a diameter of 20 mm is fabricated.