At a blustery McCain Stadium both sides settled well, but it was the Daggers who created the first goalscoring opportunity on seven minutes when a Lee Goodwin header was blocked by Boro keeper Leigh Walker.
Just four minutes later however the hosts were a goal to the good Kevin Nicholson's low cross was met by striker Tony Hackworth's left foot on the half volley. His shot came down off the Dagenham bar for Cryan to nod in the opener.
The Seadogs, clearly confident from their goal, continued to press with Hackworth shooting into the hands of Tony Roberts and defender Paul Foot hitting a drive from 25 yards which wasn't too far over the crossbar.
The pressure paid off and Boro went 2-0 up in stoppage time of the first half. Nicholson's left-foot free-kick curled into the box and found Cryan at the back post. The defender placed his header past Roberts off the inside of the post to put the home side in a commanding position.
Dagenham did their best to get back into the second half, but Walker in the Boro goal was equal to efforts from Goodwin and Scott Griffiths as the Seasiders held firm to keep their play-off dreams alive.