What does RIPA Rule 9 (Narrow Channels / Canales Angostos) require of a sports boat navigating along the course of a narrow bay channel or fairway?

1. Navigate in the exact geometric center of the channel at all times
2. Zig-zag from side to side to maintain water circulation through the cooling intake
3. Keep as near to the outer limit of the channel or fairway which lies on her starboard (estribor) side as is safe and practicable
4. Cross back and forth across the channel to alert other vessels of your presence