  Next-generation neutrino telescopes with significantly improved sensitivity
are required to pinpoint the sources of the diffuse astrophysical neutrino flux
detected by IceCube and uncover the century-old puzzle of cosmic ray origins. A
detector near the equator will provide a unique viewpoint of the neutrino sky,
complementing IceCube and other neutrino telescopes in the Northern Hemisphere.
Here we present results from an expedition to the north-eastern region of the
South China Sea, in the western Pacific Ocean. A favorable neutrino telescope
site was found on an abyssal plain at a depth of $\sim$ 3.5km. At depths below
3km, the sea current speed, water absorption and scattering lengths for
Cherenkov light, were measured to be $v_{\mathrm{c}}<$10cm/s,
$\lambda_{\mathrm{abs} }\simeq$ 27m and $\lambda_{\mathrm{sca} }\simeq$ 63m,
respectively. Accounting for these measurements, we present the design and
expected performance of a next-generation neutrino telescope, TRopIcal DEep-sea
Neutrino Telescope (TRIDENT). With its advanced photon-detection technology and
large dimensions, TRIDENT expects to observe the IceCube steady source
candidate NGC 1068 with 5$\sigma$ significance within 1 year of operation. This
level of sensitivity will open a new arena for diagnosing the origin of cosmic
rays and probing fundamental physics over astronomical baselines.
