Fig. 4. Box plots for the comparison in the maximum speed before exit between lower (white bars) and higher (gray bars) holes for each deployment. The differences in the above-water height of holes were less than 10 cm in four deployments (from 7th to 10th). ^*P<0.05; ^**P<0.01; ^***P<0.001; two-tailed Mann-Whitney U tests; n.s., not significant.