You cannot equalize the air pressure in swim googles like you can in a scuba mask. If you dive too deep you may get some "raccoon eyes" from the pressure. If you go deeper you may cause some blood vessels to rupture giving you red, bloodshot eyes. I don't think 13 feet wil be too bad but 30 feet my not feel too good. Buy or borrow a scuba mask if you can. You can let air out of your nose to equalize the pressure in the mask.