Grouped by the Grunt most likely to acquire them ... acquired by Grunt #2
I (GooRoo) believe that Gaby intended each Grunt to 'clean out' the big pool of water nearest them.
As I (GooRoo) solved it, Grunt #2 acquired Grunt #3
's and Grunt #5 
's pool Coinz.The assumption is that the solver workz with a Grunt until he is 'stuck' before working with another Grunt.
(BTS).
that was submerged 
at the start.. that was submerged at the start. that was submerged at the start. that was submerged at the start. (He leavez his island.) is busy filling in Holez 
and digging up Moundz 
, so he roamz around.In plain sight on a BT
that is submerged 
half the time in the pool near Grunt #3 's island. that is submerged half the time. that is submerged half the time. that is submerged half the time. that is submerged half the time. that is submerged half the time. that is submerged half the time. that was submerged at the start near Grunt #3 's island. that was submerged at the start, same island. that was submerged at the start, same island. that was submerged at the start, same island.
(QMS). (Assistz Grunt #4.) that was submerged at the start near Grunt #4 
's island. that was submerged at the start, same island. that was submerged at the start, same island. that was submerged at the start, same island.. (Assistz Grunt #4.) hasn't been baked yet, so he roamz around.In plain sight on a BT
that is submerged half the time in the pool near Grunt #5 's island. that is submerged half the time. that is submerged half the time. that is submerged half the time. that is submerged half the time. that is submerged half the time. that is submerged half the time. that was submerged at the start near Grunt #5 's island. that was submerged at the start, same island. that was submerged at the start, same island.. (Assistz Grunt #5.) that was submerged at the start, same island.