Some aspects on jamming of acoustic underwater communications are explored in this study. We investigate: 1. Is there any underwater communication to detect and to jam? 2. Are there situations where jamming is motivated? 3. What is the risk of being detected when communicating? 4. How sensitive to jamming are some modern methods of underwater communication? 5. What is the risk of being jammed? 6. How should we communicate in order to reduce the risk of being jammed? 7. How should we communicate in order to reduce the effect of jamming? Some conclusions from our study are: In order to reduce the risk of being jammed, short data packages should be transmitted intermittently using high data rate. If we, in spite of this, become jammed we can decrease the effect of jamming by switching over to a low data rate mode using spread spectrum and Turbo coding. Then the jammer must come very close to the receiver in order to obtain any effect.