救生船 covers both the small craft ships carry to evacuate passengers (English 'lifeboat') and dedicated rescue vessels patrolling waters (English 'rescue boat'). Smaller version:
救生艇 (jiùshēngtǐng) —
艇 specifically means a small/light vessel, so
救生艇 is the more technical word for the davit-launched lifeboat. The
救生 prefix gives you a whole family:
救生衣 life jacket,
救生圈 life ring/buoy,
救生员 lifeguard.
