The 'sorry' addition is what is funny about this sign. Signs are designed to state information clearly and professionally and the 'sorry' gives the sign a human element that is uncharacteristic. JOKE EXPLAINED.
This sign is funny in that it states the obvious problems associated with a sign advertising a temporary issue. JOKE EXPLAINED.
This sign is less funny and more a statement about how much the sign owner values sarcasm. JOKE EXPLAINED?
This sign is funny because a warning of this nature is largely superfluous. JOKE EXPLAINED.
What's funny about this sign is that there is a perceived extreme threat (the shark) that is given as a reason to do something small and annoying (peeing in the pool). JOKE EXPLAINED.
This picture is funny because the person who made the sign was clearly frustrated enough about this problem to make a sign about it. JOKE EXPLAINED.
The original sign creator being 'shut down' by the second sign creator in such a forceful manner is what causes this exchange to be funny. JOKE EXPLAINED.
This sign is using bright colors and a warm font to justify laziness which is a funny clash of context. JOKE EXPLAINED.
This sign is funny contextually because usually when someone is memorialized it's because they love that place or thing. Not so with this plaque. JOKE EXPLAINED.
The addition of the fine is what causes this sign to be funny. Once you are dead, charging you a fine seems unnecessary. JOKE EXPLAINED.