Collegiate Bests:
| Event | Score | Date | Site/Opponent |
| 50 Free | 20.62 | 3/1/25 | Big Ten Championships |
| 100 Free | 43.61 | 3/1/25 | Big Ten Championships |
| 200 Free | 1:35.06 | 2/28/25 | Big Ten Championships |
| 100 Breast | 53.87 | 11/22/24 | Ohio State Invitational |
| 200 Breast | 1:59.24 | 12/3/23 | Big Al Invitational |
| 100 Fly | 51.91 | 12/2/23 | Big Al Invitational |
| 200 IM | 1:46.10 | 12/1/23 | Big Al Invitational |
| 400 IM | 3:48.98 | 3/1/24 | Big Ten Championships |
Career records/notables: Helped PSU to post the fifth-best time in program history in the 400 Freestyle Relay (2:52.85).
2025-26 (Junior) -
Meet-By-Meet: St. Bonaventure (10/9): Placed second in the 100 Freestyle (45.11) and 200 Freestyle (1:40.56)…Helped PSU to a win in the 400 Freestyle Relay (2:56.97). Yale (10/18): Secured third in the 100 Freestyle (45.34). Ohio State Invitational (11/18-21): Helped PSU to finish eighth in the 800 Freestyle Relay (6:24.85). at Virginia (1/10): Finished fourth in the 100 Freestyle (44.35). at Princeton (1/24): Recorded a third-place finish in the 100 Freestyle (44.44) and a fourth-place finish in the 200 Freestyle (137.69). at West Virginia (1/30): Placed third in the 100 Freestyle (45.08) and 200 Freestyle (1:39.35). George Washington (1/31): Took second in the 100 Freestyle (44.03) and 100 Breaststroke (54.87)…Helped PSU to a win in the 400 Freestyle Relay (2:55.60). Big Ten Championships (2/25-28): Posted times of 43.97 in the 100 Freestyle, 1:39.68 in the 200 Freestyle and 54.09 in the 100 Breaststroke.
2024-25 (Sophomore) -
- Navy (10/4): Touched third in the 200 IM with a 1:52.55.
- Pitt (10/25-26): Finished fourth in the 100 Breast with a 55.97.
2023-24 (Freshman) -
- Navy (10/7): Posted a third place finish in the 200 Breast with a 2:04.60.
- Big Al Invitational (12/1-12/3): Swam a personal best time of 1:46.10 in the 200 IM, good for a fourth place finish and NCAA B Cut. Added another third place performance in the 400 IM with a 3:49.48, good for an NCAA B Cut. Tallied two other career bests in the 100 Breast with a 55.10, and the 200 Breast with a 1:59.24.
- Army (1/12): Touched fourth in the 200 IM and 200 Breast.
- B1G Championship (2/29-3/2): Competed in the 200 IM and 200 Breast. Added a personal best finish in the 400 IM with a 3:48.98, good for a B Cut finish.
High School
During Slavica's high school career at Ekonomaska, he was a Croatian national record holder.
Personal
Slavica is the son of Marijo and Ivana and has a younger brother David. Before attending high school, Slavica swam for his hometown club of PK Sibenik.