Aquanaut (Interceptor)

Aquanaut (Interceptor)
Title screen of the game
Game No.	524
Voting	5.60 points, 5 votes
Developer	Ian Gray
Company	Interceptor Software
Publisher	Interceptor Software, Softgold (Eurogold), Sonnenverlag
Musician	Chris Cox
HVSC-File	/MUSICIANS/C/Cox_Chris/Aquanaut.sid
Release	1984
Platform	C64
Genre	Shoot'em Up
Gamemode	Single player
Operation
Media
Language
Information	Also released in a bundle German version published in 1985 under the title "U-Boot" by Sonnenverlag

Description

The player-controlled submarine

In the game "Aquanaut", the player must pilot a submarine through an underwater cave system guarded and defended by numerous enemies. Points are awarded for shooting down enemies as well as for traversing individual sections of the labyrinth as quickly as possible. The player's mission is complete when they have dived their submarine to the deepest cave and then returned safely to their base.

Backstory

In the depths of the sea, the submarine pilots of the Aquanaut patrol maintain law and order. Their submarines are armed with torpedoes and depth charges and are considered invincible — until now, as they venture into the caves of Shallic, where the forces of evil have gathered, aiming to conquer the oceans. In the fight against underwater tanks, heat-seeking missiles, hovering minelayers, and their mines, all but one Aquanaut pilot have perished. Will this one pilot manage to penetrate to the deepest cavern and return safely to his base?

Design

Both in the intro and during gameplay, the game status is displayed in a text line at the top of the screen, consisting of the score, number of lives, and remaining bonus. Below this, a section of the underwater cave system is shown in a 304 × 176 pixel image (scrolling in all directions in increments of 2 pixels). The labyrinth's color scheme is rather monotonous, featuring dark blue rocks with white outlines on a black background; only the enemies are colorfully rendered.

Graphics

All screen content is displayed in multicolor text mode (video RAM at address $0400). The character set for the underwater labyrinth's elements is located at address $0800; for the status bar at the top of the screen, a raster interrupt briefly switches to a second character set at address $3000. The player-controlled submarine is represented by sprite 0, and friendly projectiles by sprite 1. The other sprites are used for enemies and enemy projectiles. Locks that periodically block passages are incorporated into the text display. When detecting hits and collisions with enemies, the game relies on the VIC's sprite-to-sprite collision detection (register at address $D01E), and for potential contact with rocks and locks, it relies on sprite-to-background collision detection (register at $D01F).

Sound

A three-part melody plays on the title screen. During gameplay, however, only the first two voices of the SID are used to play two background melodies; the third voice, with the help of the noise generator, underscores gunfire and explosions (see also section "Theme").

The first enemies attack shortly after launch.

Narrow passages demand precise control...

...and multi-stage locks also require exact timing.

Hints

Screen Layout

Typical scene from the game

Controls

Aquanaut is launched by pressing one of the number keys 3  to 9  to determine the initial supply of submarines. After this key press, control is exclusively via joystick, and the player sets off on their mission with the first submarine (and with 2 to 8 additional submarines as reserves):

•  : Submarine moves left/right.
•  : Submarine ascends.
•  : Submarine dives.
• : Fires a torpedo in the corresponding direction when the submarine is pointing right or left. If the bow of the submarine is pointing towards the player, pressing the fire button releases a depth charge.

Pressing any key pauses the game, but the music continues playing; pressing the key again resumes the game. Pressing RESTORE  quits the game and returns to the title screen.

Enemies

The following enemies and projectiles make life difficult for the player as they make their way through the underwater labyrinth. Successfully defeating enemies earns different rewards:

250 points

250 points

250 points

250 points

100 points

100 points

100 points

80 points

40 points

20 points

Tips

• The homing bombs launched by the underwater tanks can only be countered by hiding behind a rock, causing the bomb to collide with it and explode on its direct path to its target (left image in the gallery below), by guiding it into an airlock, or by outrunning it until it reaches its maximum range.
• The enemy's movement patterns are always the same, so it is worthwhile to develop precisely planned defensive strategies in certain situations. For example, the first enemy always appears in the same place and at the same time — and can be reliably destroyed by firing a single shot as soon as the rock formation with the small hump reaches the left edge of the screen (right animation).

The homing bombs can only be countered by luring them against a rock.

Targeted takedown of an enemy through precise timing.

Solution

The objective of "Aquanaut" is simply to traverse the entire cave system without having all of your own submarines destroyed by the enemy. There is no need to defeat a specific number of opponents or collect anything: the game ends as soon as the player-controlled submarine returns to its starting point after completing a circuit of the labyrinth or re-enters the second section of the labyrinth.

To achieve a good result or even successfully complete the mission, the player must first memorize the exact sequence of all battles and then precisely reproduce these planned gameplay sequences. A video clip can serve as inspiration for determining the optimal approach.

The game is successfully completed and ends when the player returns their submarine to the starting point...

...or re-enters the second area during another circuit through the labyrinth.

Instead of a victory celebration with fanfare, the successful submarine pilot is greeted with a simple "GAME OVER".

Map

The following graphic shows the complete game board of "Aquanaut" (without locks). The path to be traveled by the player's submarine starts in the harbor basin in the upper left corner, initially runs just below the surface to the far right, and from there descends in a zigzag pattern to the lowest level. From the lower left corner, it then goes vertically upwards back to the starting point.

The circuit through the underwater labyrinth is divided into 10 sections, each of which is rewarded with a bonus for being completed quickly. In the following map, these sections are alternately colored yellow and green; each time the boundary to the next area is crossed, the amount displayed by the counter in the upper right corner of the screen is added to the player's score. This counter then displays the bonus for the newly entered section by counting down from 1999. If the player loses a life, the next attempt starts at the beginning of the current cave section.

Cheats

In the CSDb there are two cracks with a trainer function. The Crack by FMAN (first image in the following gallery) is particularly interesting, as it offers the option of unlimited spaceships or invulnerability: Unlimited spaceships are activated and deactivated with the 'Y' and 'N' keys, respectively; the 'I' key toggles invulnerability on and off.

FMAN Trainer

ASS Trainer

Internal Data Structures

For developing custom trainer functions and for analyzing or manipulating the data used by the game, knowledge of memory allocation and internal operation is helpful. The following table therefore compiles a range of information about Aquanaut.

Address	Content	Comments
$034F	Number of submarines	Value range 0...9
$03D0	X-scrolling low	Least significant 3 bits of VIC register $D016 (XSCROLL), incremented or decremented in 2-pixel increments
$03D1	X-scrolling high	Number of characters scrolled in the X direction, value range 0...160
$03D2	Y-scrolling low	Least significant 3 bits of VIC register $D011 (YSCROLL), incremented or decremented in 2-pixel increments
$03D3	Y-scrolling high	Number of characters scrolled in the Y direction, value range 0...77
$03D5	Current section	Value range 0...9
$03D7	Highest section entered	Value range 0...9
$03DA-$03DB	Current bonus	Least significant byte first, value range 0...1999
$03E6-$03E7	Score	Least significant byte first, value range 0...65530

Votes

Voting of the C64-Wiki users (10=the best vote):
5.60 points at 5 votes (rank 965). You need to be logged in to cast a vote.
C64 Games	5	November 30, 2025 - "befriedigend" - 19950 downs
Lemon 64	5,38	November 30, 2025 - 21 votes
Ready 64	5	April 9, 2024 - 2 voti
Home Computing Weekly	3/5 (Instructions 15%, Playability 70%, Graphics 75%, Value for money 80%)	Issue 71 (July 17-23, 1984)
Personal Computer Games	6/10 (Graphics 7/10, Sound 8/10, Originality 7/10, Lasting interest 4/10)	Issue 8 (July 1984)
Universal Videogame List	2.5/5	April 9, 2024
Rombach	8	September 1984 - "Verdict 2"

Critics

Stephan64: "Given the overwhelming number of enemies clustered in the caves of Shallic, one really wonders why the Aquanauts patrol didn't intervene sooner — and now, when it's almost too late, the player on the C64 is once again expected to pull the cart out of the mud. I completely understand anyone who isn't motivated in the long run by the pretty background music and turns their back on the dark, monochromatic underwater labyrinth as quickly as possible. However, considering its early release year of 1984 and the pleasant musical accompaniment, I'll still give it a generous 5 points."

Rombachs C64-Spieleführer: "In terms of design, it's quite comparable to Zeppelin or Fort Apocalypse, perhaps even better. The high difficulty level is a drawback. Recommended for players who have already completed Zeppelin or Fort Apocalypse (rating 2)."

Miscellaneous

Cover

Cassette version cover

Inlay

Cassette version inlay

Cassette

Cassette

Theme

While the title screen is displayed, the song "What shall I do with a drunken sailor" plays in three parts. The game, however, is accompanied by two alternating two-part melodies, leaving one channel of the SID free for sound effects that underscore the gameplay. The following gallery shows these musical pieces in standard musical notation. For creative reuse, the sheet music for all melodies is also available as a PDF document (File:Aquanaut Theme PDF.pdf) and in ABC musical notation (File:Aquanaut Theme.abc.txt).

Sheet music of the title theme, reconstructed by logging all write accesses to the SID

Sheet music of the first accompaniment melody for the game

Sheet music of the second accompaniment melody

Fastloader

The cassette version of Aquanaut uses an integrated software fast loader, which is first loaded and activated as a 318-byte program named "P1" using the Kernal's cassette routines. It then reads two unnamed program segments into the address ranges $0800–$8008 and $8009–$D000, makes some modifications to the program code, and finally starts the game by jumping to address $6182. There is no loading screen or other graphic or sound effects during the loading process. Rather, the fastloader's code, stored in video RAM, is briefly visible before the screen — as is customary with the C64 operating system's cassette routines — switches off and becomes monochrome.

Thanks to optimized encoding (shorter intervals for 0 and 1 bits, no parity bit, no duplicate storage of program data — although provided as an option in the program code), loading Aquanaut takes less than three minutes, whereas the KERNAL's cassette routines would require more than a quarter of an hour for a program of this size.

The routines for synchronization and for reading a bit and a byte are identical to those in the fastloader of the games "Loco" and "P.C. Fuzz", and largely identical to those of "Elidon".

The filename on the cassette still contains some control characters, so the usual "FOUND AQUANAUT" message does not appear.

Unfortunately, the second part of the fastloader is located in the video RAM.

Video Recording

Complete playthrough of the game.

Bugs

During each phase of the game — including the final section, immediately before returning to the starting point — a countdown timer appears in the upper right corner, indicating a bonus for successfully completing the current section. At the end of the game, the player does not receive a credit equal to the score; instead, the game ends abruptly without any further changes to the score.

The promised bonus of 1505 points is withheld from the player at the end of the game.

Trivia

In the game "Aquanaut", the high score list is not a separate page but rather part of the labyrinth: Shortly after starting, in the upper right corner of the cave system, the player passes the initials of their most successful predecessors in their submarine. Further along the way, they encounter a series of more or less motivating sayings on the rock walls, such as "HALFWAY THERE", "PLEXAR WAS HERE TOO", and "DROWN A MUTANT CAMEL TODAY."

Highscore

The following list invites players to immortalize themselves with their highest score. To ensure comparability of the results, the game should be started with a total of 9 submarines.

Topscore of Ivanpaduano

1. Ivanpaduano - 6636 (06.10.2024)
2. Stephan64 - 2267 (13.04.2024)
3. Nobody - 0 (tt.mm.jjjj)

	#2 Stephan64		#3 Nobody

Links

• C64Games.de - Game No. 2717 (Aquanaut)
• C64Games.de - Game No. 2252 (U-Boot)
• Lemon64 - Game No. 3016
• Gamebase64.com - Game No. 347
• C64.com - Game No. 678
• ready64 - Game No. 52
• CSDb - Release No. 50944
• Aquanaut (Interceptor) at MobyGames

• Universal Videogame List

Magazine

• Home Computing Weekly test report (p. 22)
• Personal Computer Games test report (p. 37)

Videos

• Video at YouTube von Renaldo Lo Muto