You can get Marine Bands that feel a bit leaky and it's tempting to soak them, but you can't control which way all those little partitions are going to swell and shrink back and you end up doing more harm than good. I hate to say it, but you have plenty of alternative choices of harmonica these days, at similar prices to those pesky MBs, which are generally more comfortable and less leaky (and screwed, not nailed together, so easier to look after). Soaking harps with plastic combs is totally pointless. The modern Hohner Blues Harps (with MS stamped on their covers) use a different type of wood that is far less prone to swelling, so soaking those is pointless as well. MB Deluxe models (dearer) have sealed wooden combs which also resist swelling. Soaking pointless again. There's no final consensus as to which comb material is better for sound but no serious study so far has found any significant differences. Go for plastic! More durable, more comfortable in the mouth and much easier to clean.