That land is an Island in addition to its other types for as long as it has a flood counter on it
On the flipside, you do get Menace, and hes a two-power Legendary, meaning he slots into a bunch of the sweet Mardu brews, from Alesha to Terra
Time range: Several months to a couple years, depending on the card
There are plenty of quality cards that synergize well with Herald of Secret Streams, and you dont have to work hard to have creatures with +1/+1 counters in this format
CORI-JP004 Gurifoh DARK Fiend / Effect LV1 300/200 You can only use the 1st effect of this cards name once per turn
If you were to have a land type count as that color instead, you would allow Mtenda Lions and such, but disallow many more things