波がそのボートを飲み込んでしまった。

wave

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

that (something or someone distant from the speaker, close to the listener; actions of the listener, or ideas expressed or understood by the listener); the; um...; er...; uh...

board

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to gulp down; to swallow deeply; to understand; to take in; to catch on to; to learn; to digest; to engulf; to swallow up; to be filled with (people); to be crowded; to hold back from saying something; to swallow (one's words)