generally - two ways
A pump out station to which you must go. Or a portable pump out that comes to you. That latter can be a honey wagon on a boat.
ISPA Yachtmaster Offshore Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
ASA 201, 203, 204, 205, 206, 214
As I sail, I praise God, and care not. (Luke Foxe)