This is, in my opinion, the ultimate refreshment for those still, hot summer afternoons when you just want to lie there, unmoving, until the weather changes. Frozen watermelon, when blended, creates a fine, velvety slush very much like a slurpee. Add a little mint and lime and you’ve got an ultra-refreshing, natural slushie. Oh, and a little rum doesn’t go amiss either, if you feel like turning it into a frozen watermelon mojito.