[falconmaster]

If you sand it epoxy works great. We use 1/4" bolts with 3/8" lock nuts, and it works great. We use all the same size nuts and bolts. You need stainless for the underwater bots!

In most cases the cost is more, but not that much more, especially if you count in the labor time and repair time you save.
1 1/2" x 1 1/2" x 1/4" is $2.74 a foot

1" x 1" x 1/8" $1.20 per foot

6" c-channel $7.34 per foot

The water has no effect on the material at all!