Linear　chirp-based　underwater　acoustic　communication　has　been　widely　used　due　to　its　reliability　and　long-range　transmission　capability.　However,　unlike　the　counterpart　chirp　technology　in　wireless　-　LoRa,　its　throughput　is　severely　limited　by　the　number　of　modulated　chirps　in　a　symbol.　The　fundamental　challenge　lies　in　the　underwater　multi-path　channel,　where　the　delayed　signal　may　cause　inter-symbol　and　intra-symbol　interfere.　In　this　paper,　we　present　UWLoRa+,　a　system　that　realizes　the　same　chirp　modulation　as　LoRa　with　higher　data　rate,　and　address　the　multi-path　challenge　via　the　following　new　designs:　a)　we　replace　the　linear　chirp　used　by　LoRa　with　the　non-linear　chirp　to　reduce　the　signal　interference　range　and　the　collision　probability;　b)　we　design　an　algorithm　that　first　demodulates　each　path　and　then　combines　the　demodulation　results　of　detected　paths;　and　c)　we　replace　the　Hamming　codes　used　by　LoRa　with　the　non-binary　LDPC　codes　to　mitigate　the　impact　of　the　inevitable　collision.　Experiment　results　show　that　the　new　designs　improve　the　bit　error　rate　(BER)　by　3　times,　and　the　packet　error　rate　(PER)　significantly,　compared　with　the　LoRa＇s　naive　design.　Compared　with　an　state-of-the-art　system　for　decoding　underwater　LoRa　chirp　signal,　UWLoRa+　improves　the　throughput　by　up　to　50　times.