Never seen these until today.  I think they are called currach oars.  Massive.  What is the reason are made such way ?  Appear to be poorly efficient.

4 minutes ago, Externet said:

What is the reason are made such way ? 

Maybe exercise, like putting a mask across your face while running to increase difficulty and improve lung training?

Edited August 22, 20187 yr by iNow

Like 10 cm x 10 cm square, like 3+ metres long, no paddle end.

Edited August 22, 20187 yr by Externet

Says online for dealing with rough ocean waves better.

http://www.annapolisirishrowers.org/history.asp

Curious how will it works.

Yes, saw that explanation; but Irish are not the only ones dealing with rough seas;  never seen tribes from Oceania rowing for centuries using anything similar.  Oars are aimed to be light, efficient, paddle areas/surfaces to match average muscles.

Thinking might work better to maintain synchronization in rougher conditions. More oar in the water making up the difference in surface area.

Did you run across the link below yet?

http://www.ybw.com/forums/showthread.php?475721-Currach-oars

Sounds like they hold their own pretty well.

Yes, that was the first search result I opened.  Surprising.  Still cannot believe the efficiency part...

If you have a bladed paddle, you have to get it at the right angle to get the expected pull, whereas the curragh oar can be used at any angle, and you get the same amount of drag. When you watch the varsity boat race, they have trouble in rough water on the back stroke with the blades catching the waves. That's just on the River Thames, so it might be worse at sea with much bigger waves.

That's my theory anyway. I always thought those oars looked odd, but maybe they just work better that way.

Edit :

Maybe those paddles last longer too. They are less fragile than a blade, so would probably survive hitting rocks, and being tossed around on shore. They would have a rough life around the Atlantic shores being used for fishing. 

Edited August 22, 20187 yr by mistermack