Load, capacity and freeboard
Count yourself, your gear and anything you carry against the maker's capacity (REI). A common rule of thumb is to stay under about 70% of the maximum so the kayak keeps enough freeboard (height above the water) to handle waves and stay responsive. Kayaks and canoes don't carry Coast Guard capacity plates, so use the maker's number. Load calculator
Educational summary of the cited sources, not a safety guarantee. Check local conditions and wear a life jacket.