Mobile platforms such as iOS are still too limited to support complex submarine sims such as Silent Hunter or Dangerous Waters but some offerings for the iPad, Android, Kindle  Fire, and other similar devices have some games which are entertaining and almost realistic. Crash Dive is not only enjoyable but can be challenging at the sim level of play. Codeknitters has attempted a realistic tour of duty in the Pacific during World War II in a Gato/Balao class sub with Silent Depth. If you remember Silent Service II and the original Silent Hunter, you will be interested in Silent Depth.

The graphics are actually quite good. Interior views allow players to "walk" around the control room and the bridge while a specific exterior view shows the sub in 3D from all angles. Facilities at the home port of Midway are finely done down to the underwater wreck of somebody's warship. Pretty as these graphics are, they have nothing to do with game play. Fortunately, gauges and dials that actually do something are arranged at the bottom and sides of these screens. These gauges mark fuel, battery and compressed air levels while depth, speed and heading are shown in others. A wheel changes course and a telegraph sets speed. A compass in the upper right hand corner graphical depicts both the sub's heading and the captain's view. Along with these features, the seven buttons for stations such as systems, periscope, map, Target Bearing Indicator (TBT) and deck gun are always visible. While the controls are a bit crowded (limited screen space is determined by device size), the game functions are still manageable.

Environmental conditions such as sea state, rain and visibility are well-portrayed. The sun and moon rise and set with great effect on visibility as clouds drift across the sky. Moonless nights are pitch dark but clear ones are starry and bright. Surface ships are shown in detail at close ranges and show blasts, smoke and fire when hit although not as dramatically as in other games. Torpedo wakes are clear as are the wakes of their targets that try to dodge them.

Sounds are gurgles for tank flooding, hisses as torpedoes launch, blasts indicating hits, bells for surfacing, "Aooga!" for diving and deck gun fire not to mention the inevitable sonar pings. Nastier sounds are the explosion of depth charges and the shriek of incoming shells. Voices are limited announcing "Battle stations", flooding dive tanks and reporting actions of attackers but crew messages flash on the screen with speed/course changes and damage reports. The manual and in-game training scenario do a good job explaining the interface and functions.

Silent Depth doesn't have short missions, just one long war patrol. Play starts with the craft leaving Midway where players can opt to manually conn their way out of the harbor. A quicker method is to click the map button to bring up the global map. This map covers the Central Pacific with most important islands shown. Also exhibited are analog values for fuel, battery and air levels. A clock shows the time as does an analog display. The date is present -- important as one sub can sail throughout the war if it survives. The submarine's position is seen as a tadpole-like black graphic. The patrol area is designated with a black outline and a course there can be designated with a screen tap. Time can be compressed from 1x up to 32x. The shading on the map changes to red during nights. During transit, players should take time occasionally to view the systems screen to check on the eleven different departments such as engineering and both torpedo rooms. An excellent innovation seen here is a water temperature gauge so players can find thermoclines to hide beneath.

On the way to the patrol zone on the surface, the sub will encounter single ships. A message appears relating target size, course bearing and speed. Equally important is the time and visibility since attacks at night in mist are a waste a time. Small targets present a problem for skippers. They aren't worth one or two of the twenty-four torpedoes on board but could be sunk with gunfire. However, the deck gun is subject to the pitch and roll of swells, making hits at any but close range unlikely. Closing range costs precious diesel fuel so, unless small targets start near to the sub, they should be given a pass.

Medium targets are another matter and attacks on them show the game's realism. Both the periscope and TBT are swiveled by swipes with the periscope also having arrows for more precise movement; each has a magnification up to 8x and degree marks on the reticule. These degree marks represent a bug as they are out of sync with the headings shown in the compass' view and course bearing. Centering on a target shows its range, course and speed. Presumably, these numbers are put into a "banjo" or TDC behind the scenes for your targeting solution. A small triangle under the target is colored yellow for new targets, green for good solutions and red for no solution. Maneuvering for a shot requires handling the wheel to line up on the target and the wheel must be put amidships to steady a run. When a torpedo is launched, a stop watch shows running time and when the hit should occur. Another method to maneuver is to put a waypoint on the tactical map and compress time from real to 32x. Realism is further enhanced by the fact that even the best solutions have a 10% chance of failure and targets often require two or three torpedoes to sink. Hits are made even more difficult to make as the AI is very good at evasion.

Once in the patrol zone, small convoys appear. The tactical map comes into its own here as waypoints are used to get in position for the kill. Waypoints are added with a screen tap. The red enemy icons move in a straight line but, if one breaks off and heads for the sub, they had an escort! Since "down the throat" shots are suicidal, players can do one or two things to escape; players can either dive and twist away from the enemy or dive even deeper, stop engines and pretend to be a rock on the bottom. Depth charges will greet you with a vengeance. Damage can be viewed in the systems screen and sometimes be repaired. The worst damage is a fuel leak or wrecking the compressed air system. If either of these is emptied, the boat is doomed.

Resupply can only be done at the home port, so fuel level is the real incentive to go home even if some torpedoes remain. Small targets on the way back can be a good way to use the remaining "fish" and pad the tonnage score. Resupply and needed repairs are done and medals given for extraordinary performance.
Technical problems may arise. On an iPad 2 in the first attempts to play, the game crashed at least 90% of the time when running on battery. The work-around was to play the game plugged into the charger. The game has worked flawlessly ever since on battery. Still, the game puts a load on the battery. Playing the game on Android devices and a Kindle Fire has been picture-perfect and crash-free.

Summary
Silent Depth continues to be upgraded with anti-aircraft guns among other things. Despite minor flaws such as the out-of synch degree marks and lack of decoys, this game is about as realistic as is possible on mobile apps. There's more than a bit of Silent Hunter I nostalgia here, with the advantage of being portable. The attempt is admirable but while the execution is a bit flawed, gamers are guaranteed hours of entertainment hunting Imperial Japanese convoys.

Developer: Codeknitters

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