Purpose: To examine the effects of 6 weeks of training cessation on young swimmers’ anthropometrics, in-water force, performance, and kinematics according to biological maturation. Methods: Eighteen swimmers (7 girls: 12.43 [0.73] y old; 11 boys: 13.27 [0.79] y old) were assessed pretest and posttest 6 weeks apart. Body mass, stature, arm span, and hand surface area were measured as anthropometric parameters, and biological maturation was estimated (ie, peak height velocity [PHV]). The in-water force was retrieved during 2 bouts of 25-m front crawl, allowing the estimation of the symmetry index. The time to complete the 25-m was considered the performance outcome, whereas velocity, stroke rate, stroke length, stroke index, and arm stroke efficiency were used as kinematic parameters. Results: All anthropometric parameters increased during the detraining period. Although the in-water force remained unchanged, the magnitude of the effects was large for the symmetry index (P = .021; d = 0.87). For the pooled sample, neither performance nor kinematics changed after detraining, but the stroke index increased (P = .054; d = 0.27). Pre-PHV swimmers showed unchanged values in all parameters, despite natural growth. Mid-PHV swimmers showed a similar trend in addition to reductions in stroke rate (P = .040; d = 0.60) and increases in stroke length (P = .043; d = 1.00). Conclusions: In-water force, performance, and kinematics (25-m front crawl) were not impaired after 6 weeks of training cessation in a group of young swimmers. Given interindividual and intraindividual differences according to maturity status, coaches should be aware that distinct trends within the group can be found.