founder, flounder

Founder or founder, said of a ship, means to fill with water and sink--
The sailors abandoned the ship when it began to founder.
The ship may founder if we stop pumping; keep at it!
Founder or founder also means one of the persons who first established or founded an organization--
We have asked the founder of the firm to retire, and let the board run the business.
The founder of the library will make a speech at the next meeting.
Founder may be used to describe a sinking building--
A building this size may founder more than a foot without any serious damage.
Founder is also used to describe a horse, or some other animal, that can't get up because of an injury or illness--
The horse is favoring one leg; if we don't give him a rest he may founder.

Flounder or flounder means to struggle clumsily or in confusion--
I can't stand here and watch him flounder about, like a turtle on its back.
When he began to flounder in panic, the lifeguard jumped in and hauled him out.
Flounder may also mean the popular edible fish--
Let's have fried flounder for dinner.
There's a sale on flounder at the fish market.

Now that you know that, you can say--
"The ship seemed about to founder, when a sailor got caught in the rigging and began to flounder."

Note--not to be confused with "found her", meaning came upon by searching or by chance ( found ) someone female ( her)--
I looked for Mom for an hour before I found her.