A vessel constrained by her draughtThe term 'vessel constrained by her draught' means a power-driven vessel which because of her draught in relation to the available depth and width of navigable water, is severely restricted in her ability to deviate from the course she is following. may, in addition to the lights prescribed for power-driven vesselsThe term 'power-driven vessel' means any vessel propelled by machinery. More in rule 23, exhibit where they can best be seen three all-round red lights in a vertical line, or a cylinder.