The direction of the current is indicated by the direction that the whirlpools are rotating.
Whirlpools can become a problem when a passing player is thrust into an explosion, monster, or other hazard. Players can also potentially be shot into dead ends, from which the only escape is either death, a time-up, or aid from player on the outside who can clear a path of Soft Blocks to get the trapped player out.
In Bomberman '94, they appear as the Dash Roller (ダッシュローラー) trap, comprised of two rotating tires.
In Bomberman World, Ocean Currents appear both in their original form and as tornados on dry land. Underwater currents in this game allow Bomberman to cross gaps.
1. Super Bomberman 3 Japanese manual, pg. 17
2. Bomberman '94 Japanese manual, pg. 9