These are called "earth anchor".

Grainger has these available online.

Here in FL you can generally find these in different sizes at ACE Hardware.

I agree with previous posters about "anchoring" the boat...makes me sleep better.

I have an 3 "anchors" depending on soil makeup.

• Dog Screws for very hard soil.
• Earth Anchor for soft(er) soil
• 2 x 4 to bury in sand