Hydra is a bidirectional transfer protocol, that is: you can download AND upload at the same time, while additionally chatting with the remote side. There is almost no drawback on the transfer efficiency, however, it might happen that chatting slows things down, or very bad lines make it necessary for the Hydra program to auto-switchback to unidirectional transfer.
Since CNet has no built-in Hydra support, this BBS uses "Hydra/3" by 1oo%, which is an excellent implementation for CNet.
How to do: mark the files you want to download just as usual. When you are finished, enter the Hydra-Temp area in the Up-/Download Base ("U" from the main prompt, then the appropriate area number), and enter "HY" to start the BBS'es HydraCom.
Usage depends on the comms software you are using. There exist numerous implementations of Hydra for almost every comms package on the Amiga. If you have no Hydra support for your comms program, try to "FIND hyd" from the main prompt, or "BG 'hyd'" from the UDBase root prompt.