[NamTaf]

2 reasons:

1) As you say, salt water is bad. Do never go in salt water if you want metallic, electronic things to keep working.

2) The rocket can't withstand much, if any, load in longitudinal bending mode. It'll buckle like a toilet paper cardboard tube. This almost certainly includes under its own weight, if you were to 'catch' it at the top of the rocket and hold it on an angle. To design against that, you'd be adding way too much weight to the structure to make it worthwhile.