Cement anchors??? This is really odd. If I owned such a small boat, I'd want to use of the ultra lightweight aluminum-magnesium Fortress anchors. A small one only weighs about 4 lbs. and has great holding power. They are not cheap, however. An inexpensive alternative can be bought for about $10 but is about 50% heavier.
I had wondered about that also .That boat is a dingy it seemed odd..but perhaps the cost was a cause