Your marine air conditioners condensation pan is overflowing.
Drain pan nipple on pan clogged. Clean nipple.
Drain hose clogged, misaligned or kinked. Fix and/or clear hose.
Air conditioner not properly elevated to drain water to drain pan nipple. Check unit mounting to insure water will flow to nipple.
If a Mermaid Condensator is being used, ensure that the filter is clean. If not, clean filter and check flow of water through Condensator. Refer to the Mermaid on-line Condensator instructions for further assistance.