This expansion was released in connection with Mayday Games’ 2012 Kickstarter campaign for their Deluxe version of Get Bit!.
You will use the Dolphin die for this expansion, as well as the special Dolphin card for each player. At the start of the game, give each swimmer the extra D card for their color, replacing the highest number in your hand. (So the swimmers should have the numbers 1 to however many players there are, plus the Dolphin card.)
When a D card is played, before swimmers are moved, that player rolls the Dolphin die. That players card is considered to be whatever number was rolled for all purposes, including tying with other dice/cards. Multiple D cards are NOT considered to tie each other unless they roll the same value.
The dolphin comes up if the player rolls a 6 but it is treated as if the player had played a "9", and the shark icon is considered a 0. As these numbers are not present on cards, they only ever tie if multiple swimmers play their dolphin card in the same round and roll the same icon.
(Dolphin Die: 2, 3, 4, 5, Dolphin(6), Shark/(0))