How was the Fishguard force supposed to cross the Severn?

How did the French plan to cross the Severn on the way from Fishguard to Bristol?

It is unclear how the planners intended to cross the Severn. The modern bridges and tunnel were unavailable in 1797.

It is unclear whether French planners worked through how the invasion force would cross the Severn. The modern Severn and Prince of Wales bridges visible on a current map did not exist in 1797, and the Severn Tunnel opened only in 1886. Any march from Fishguard therefore needed a period-appropriate crossing plan as well as a route across Wales. The unanswered crossing compounds the severe distance, terrain, supply, and winter-weather problems facing a force of roughly 1,500 troops.