Here's a close-up of one of them:
The four large characters above the fish are:
海 丰 渔 塑
Evelyne says the first two characters (from left to right) are the name of a coastal county — "Haifeng" — in southern China.
The third character means "fishery."
And the fourth character means "plastic."
Here's the second float. Both floats were ~13 cm long.
We need to take a better picture of the characters below the anchor. Then, if possible, I'll provide an update about the translation on this float.
There were also lots of other floats, buoys, and glass bottles. Could this have been debris from an offshore fishing boat?