At Japanese nuclear plant, a battle to contain radiation

Commentator at 2:40 says Using Seawater to cool fuel rods is a big mistake. He suggests that they should have used concrete to bury fuel rods rather than sea water to cool them in a failed effort to save the reactors.
I'm no expert but where the heck are they gonna get the concrete needed for this type of job and second the use of seawater to cool reactor will render it useless anyway so commentator just makes no sense.