Damn, only just noticed an error by the artist on this, she only has one breast. From what I saw on the twitter page he was running behind somehow and barely made the time to rush this work out. Would probably point it out to him but I don't have a twitter account.

Monki said:

Damn, only just noticed an error by the artist on this, she only has one breast. From what I saw on the twitter page he was running behind somehow and barely made the time to rush this work out. Would probably point it out to him but I don't have a twitter account.

There's no error. Check just a little bit upwards from said breast. It's just not noticeably big.

OMGkillitwithfire said:

There's no error. Check just a little bit upwards from said breast. It's just not noticeably big.

Ah yes I see it now, at a glance I thought it was part of the strap to her bikini top.

The word スイカさん here is not a personification, so the translation "Mr. Watermelon" is not suitable.
Japanese people sometimes add -さん to foods or other inanimate words to express politeness or friendliness (google 食べ物 さん付け for details).